use std::path::Path;
use std::str::FromStr;
use std::{fmt, mem};

use itertools::Itertools;
use thiserror::Error;
use toml_edit::{
    Array, ArrayOfTables, DocumentMut, Formatted, Item, RawString, Table, TomlError, Value,
};
use url::Url;

use uv_cache_key::CanonicalUrl;
use uv_distribution_types::Index;
use uv_fs::PortablePath;
use uv_normalize::GroupName;
use uv_pep440::{Version, VersionSpecifier, VersionSpecifiers};
use uv_pep508::{ExtraName, MarkerTree, PackageName, Requirement, VersionOrUrl};

use crate::pyproject::{DependencyType, Source};

/// Raw and mutable representation of a `pyproject.toml`.
///
/// This is useful for operations that require editing an existing `pyproject.toml` while
/// preserving comments and other structure, such as `uv add` and `uv remove`.
pub struct PyProjectTomlMut {
    doc: DocumentMut,
    target: DependencyTarget,
}

#[derive(Error, Debug)]
pub enum Error {
    #[error("Failed to parse `pyproject.toml`")]
    Parse(#[from] Box<TomlError>),
    #[error("Failed to serialize `pyproject.toml`")]
    Serialize(#[from] Box<toml::ser::Error>),
    #[error("Failed to deserialize `pyproject.toml`")]
    Deserialize(#[from] Box<toml::de::Error>),
    #[error("Dependencies in `pyproject.toml` are malformed")]
    MalformedDependencies,
    #[error("Sources in `pyproject.toml` are malformed")]
    MalformedSources,
    #[error("Workspace in `pyproject.toml` is malformed")]
    MalformedWorkspace,
    #[error("Expected a dependency at index {0}")]
    MissingDependency(usize),
    #[error("Cannot perform ambiguous update; found multiple entries with matching package names")]
    Ambiguous,
}

/// The result of editing an array in a TOML document.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum ArrayEdit {
    /// An existing entry (at the given index) was updated.
    Update(usize),
    /// A new entry was added at the given index (typically, the end of the array).
    Add(usize),
}

#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum CommentType {
    /// A comment that appears on its own line.
    OwnLine,
    /// A comment that appears at the end of a line.
    EndOfLine,
}

#[derive(Debug, Clone)]
struct Comment {
    text: String,
    comment_type: CommentType,
}

impl ArrayEdit {
    pub fn index(&self) -> usize {
        match self {
            Self::Update(i) | Self::Add(i) => *i,
        }
    }
}

/// Specifies whether dependencies are added to a script file or a `pyproject.toml` file.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum DependencyTarget {
    /// A PEP 723 script, with inline metadata.
    Script,
    /// A project with a `pyproject.toml`.
    PyProjectToml,
}

impl PyProjectTomlMut {
    /// Initialize a [`PyProjectTomlMut`] from a [`str`].
    pub fn from_toml(raw: &str, target: DependencyTarget) -> Result<Self, Error> {
        Ok(Self {
            doc: raw.parse().map_err(Box::new)?,
            target,
        })
    }

    /// Adds a project to the workspace.
    pub fn add_workspace(&mut self, path: impl AsRef<Path>) -> Result<(), Error> {
        // Get or create `tool.uv.workspace.members`.
        let members = self
            .doc
            .entry("tool")
            .or_insert(implicit())
            .as_table_mut()
            .ok_or(Error::MalformedWorkspace)?
            .entry("uv")
            .or_insert(implicit())
            .as_table_mut()
            .ok_or(Error::MalformedWorkspace)?
            .entry("workspace")
            .or_insert(Item::Table(Table::new()))
            .as_table_mut()
            .ok_or(Error::MalformedWorkspace)?
            .entry("members")
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedWorkspace)?;

        // Add the path to the workspace.
        members.push(PortablePath::from(path.as_ref()).to_string());

        Ok(())
    }

    /// Retrieves a mutable reference to the `project` [`Table`] of the TOML document, creating the
    /// table if necessary.
    ///
    /// For a script, this returns the root table.
    fn project(&mut self) -> Result<&mut Table, Error> {
        let doc = match self.target {
            DependencyTarget::Script => self.doc.as_table_mut(),
            DependencyTarget::PyProjectToml => self
                .doc
                .entry("project")
                .or_insert(Item::Table(Table::new()))
                .as_table_mut()
                .ok_or(Error::MalformedDependencies)?,
        };
        Ok(doc)
    }

    /// Retrieves an optional mutable reference to the `project` [`Table`], returning `None` if it
    /// doesn't exist.
    ///
    /// For a script, this returns the root table.
    fn project_mut(&mut self) -> Result<Option<&mut Table>, Error> {
        let doc = match self.target {
            DependencyTarget::Script => Some(self.doc.as_table_mut()),
            DependencyTarget::PyProjectToml => self
                .doc
                .get_mut("project")
                .map(|project| project.as_table_mut().ok_or(Error::MalformedSources))
                .transpose()?,
        };
        Ok(doc)
    }

    /// Adds a dependency to `project.dependencies`.
    ///
    /// Returns `true` if the dependency was added, `false` if it was updated.
    pub fn add_dependency(
        &mut self,
        req: &Requirement,
        source: Option<&Source>,
    ) -> Result<ArrayEdit, Error> {
        // Get or create `project.dependencies`.
        let dependencies = self
            .project()?
            .entry("dependencies")
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedDependencies)?;

        let name = req.name.clone();
        let edit = add_dependency(req, dependencies, source.is_some())?;

        if let Some(source) = source {
            self.add_source(&name, source)?;
        }

        Ok(edit)
    }

    /// Adds a development dependency to `tool.uv.dev-dependencies`.
    ///
    /// Returns `true` if the dependency was added, `false` if it was updated.
    pub fn add_dev_dependency(
        &mut self,
        req: &Requirement,
        source: Option<&Source>,
    ) -> Result<ArrayEdit, Error> {
        // Get or create `tool.uv.dev-dependencies`.
        let dev_dependencies = self
            .doc
            .entry("tool")
            .or_insert(implicit())
            .as_table_mut()
            .ok_or(Error::MalformedSources)?
            .entry("uv")
            .or_insert(Item::Table(Table::new()))
            .as_table_mut()
            .ok_or(Error::MalformedSources)?
            .entry("dev-dependencies")
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedDependencies)?;

        let name = req.name.clone();
        let edit = add_dependency(req, dev_dependencies, source.is_some())?;

        if let Some(source) = source {
            self.add_source(&name, source)?;
        }

        Ok(edit)
    }

    /// Add an [`Index`] to `tool.uv.index`.
    pub fn add_index(&mut self, index: &Index) -> Result<(), Error> {
        let existing = self
            .doc
            .entry("tool")
            .or_insert(implicit())
            .as_table_mut()
            .ok_or(Error::MalformedSources)?
            .entry("uv")
            .or_insert(implicit())
            .as_table_mut()
            .ok_or(Error::MalformedSources)?
            .entry("index")
            .or_insert(Item::ArrayOfTables(ArrayOfTables::new()))
            .as_array_of_tables_mut()
            .ok_or(Error::MalformedSources)?;

        // If there's already an index with the same name or URL, update it (and move it to the top).
        let mut table = existing
            .iter()
            .find(|table| {
                // If the index has the same name, reuse it.
                if let Some(index) = index.name.as_deref() {
                    if table
                        .get("name")
                        .and_then(|name| name.as_str())
                        .is_some_and(|name| name == index)
                    {
                        return true;
                    }
                }

                // If the index is the default, and there's another default index, reuse it.
                if index.default
                    && table
                        .get("default")
                        .is_some_and(|default| default.as_bool() == Some(true))
                {
                    return true;
                }

                // If there's another index with the same URL, reuse it.
                if table
                    .get("url")
                    .and_then(|item| item.as_str())
                    .and_then(|url| Url::parse(url).ok())
                    .is_some_and(|url| {
                        CanonicalUrl::new(&url) == CanonicalUrl::new(index.url.url())
                    })
                {
                    return true;
                }

                false
            })
            .cloned()
            .unwrap_or_default();

        // If necessary, update the name.
        if let Some(index) = index.name.as_deref() {
            if !table
                .get("name")
                .and_then(|name| name.as_str())
                .is_some_and(|name| name == index)
            {
                let mut formatted = Formatted::new(index.to_string());
                if let Some(value) = table.get("name").and_then(Item::as_value) {
                    if let Some(prefix) = value.decor().prefix() {
                        formatted.decor_mut().set_prefix(prefix.clone());
                    }
                    if let Some(suffix) = value.decor().suffix() {
                        formatted.decor_mut().set_suffix(suffix.clone());
                    }
                }
                table.insert("name", Value::String(formatted).into());
            }
        }

        // If necessary, update the URL.
        if !table
            .get("url")
            .and_then(|item| item.as_str())
            .and_then(|url| Url::parse(url).ok())
            .is_some_and(|url| CanonicalUrl::new(&url) == CanonicalUrl::new(index.url.url()))
        {
            let mut formatted = Formatted::new(index.url.to_string());
            if let Some(value) = table.get("url").and_then(Item::as_value) {
                if let Some(prefix) = value.decor().prefix() {
                    formatted.decor_mut().set_prefix(prefix.clone());
                }
                if let Some(suffix) = value.decor().suffix() {
                    formatted.decor_mut().set_suffix(suffix.clone());
                }
            }
            table.insert("url", Value::String(formatted).into());
        }

        // If necessary, update the default.
        if index.default {
            if !table
                .get("default")
                .and_then(toml_edit::Item::as_bool)
                .is_some_and(|default| default)
            {
                let mut formatted = Formatted::new(true);
                if let Some(value) = table.get("default").and_then(Item::as_value) {
                    if let Some(prefix) = value.decor().prefix() {
                        formatted.decor_mut().set_prefix(prefix.clone());
                    }
                    if let Some(suffix) = value.decor().suffix() {
                        formatted.decor_mut().set_suffix(suffix.clone());
                    }
                }
                table.insert("default", Value::Boolean(formatted).into());
            }
        }

        // Remove any replaced tables.
        existing.retain(|table| {
            // If the index has the same name, skip it.
            if let Some(index) = index.name.as_deref() {
                if table
                    .get("name")
                    .and_then(|name| name.as_str())
                    .is_some_and(|name| name == index)
                {
                    return false;
                }
            }

            // If there's another default index, skip it.
            if index.default
                && table
                    .get("default")
                    .is_some_and(|default| default.as_bool() == Some(true))
            {
                return false;
            }

            // If there's another index with the same URL, skip it.
            if table
                .get("url")
                .and_then(|item| item.as_str())
                .and_then(|url| Url::parse(url).ok())
                .is_some_and(|url| CanonicalUrl::new(&url) == CanonicalUrl::new(index.url.url()))
            {
                return false;
            }

            true
        });

        // Set the position to the minimum, if it's not already the first element.
        if let Some(min) = existing.iter().filter_map(toml_edit::Table::position).min() {
            table.set_position(min);

            // Increment the position of all existing elements.
            for table in existing.iter_mut() {
                if let Some(position) = table.position() {
                    table.set_position(position + 1);
                }
            }
        }

        // Push the item to the table.
        existing.push(table);

        Ok(())
    }

    /// Adds a dependency to `project.optional-dependencies`.
    ///
    /// Returns `true` if the dependency was added, `false` if it was updated.
    pub fn add_optional_dependency(
        &mut self,
        group: &ExtraName,
        req: &Requirement,
        source: Option<&Source>,
    ) -> Result<ArrayEdit, Error> {
        // Get or create `project.optional-dependencies`.
        let optional_dependencies = self
            .project()?
            .entry("optional-dependencies")
            .or_insert(Item::Table(Table::new()))
            .as_table_like_mut()
            .ok_or(Error::MalformedDependencies)?;

        let group = optional_dependencies
            .entry(group.as_ref())
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedDependencies)?;

        let name = req.name.clone();
        let added = add_dependency(req, group, source.is_some())?;

        optional_dependencies.fmt();

        if let Some(source) = source {
            self.add_source(&name, source)?;
        }

        Ok(added)
    }

    /// Adds a dependency to `dependency-groups`.
    ///
    /// Returns `true` if the dependency was added, `false` if it was updated.
    pub fn add_dependency_group_requirement(
        &mut self,
        group: &GroupName,
        req: &Requirement,
        source: Option<&Source>,
    ) -> Result<ArrayEdit, Error> {
        // Get or create `dependency-groups`.
        let dependency_groups = self
            .doc
            .entry("dependency-groups")
            .or_insert(Item::Table(Table::new()))
            .as_table_like_mut()
            .ok_or(Error::MalformedDependencies)?;

        let group = dependency_groups
            .entry(group.as_ref())
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedDependencies)?;

        let name = req.name.clone();
        let added = add_dependency(req, group, source.is_some())?;

        dependency_groups.fmt();

        if let Some(source) = source {
            self.add_source(&name, source)?;
        }

        Ok(added)
    }

    /// Set the minimum version for an existing dependency in `project.dependencies`.
    pub fn set_dependency_minimum_version(
        &mut self,
        index: usize,
        version: Version,
    ) -> Result<(), Error> {
        // Get or create `project.dependencies`.
        let dependencies = self
            .project()?
            .entry("dependencies")
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedDependencies)?;

        let Some(req) = dependencies.get(index) else {
            return Err(Error::MissingDependency(index));
        };

        let mut req = req
            .as_str()
            .and_then(try_parse_requirement)
            .ok_or(Error::MalformedDependencies)?;
        req.version_or_url = Some(VersionOrUrl::VersionSpecifier(VersionSpecifiers::from(
            VersionSpecifier::greater_than_equal_version(version),
        )));
        dependencies.replace(index, req.to_string());

        Ok(())
    }

    /// Set the minimum version for an existing dependency in `tool.uv.dev-dependencies`.
    pub fn set_dev_dependency_minimum_version(
        &mut self,
        index: usize,
        version: Version,
    ) -> Result<(), Error> {
        // Get or create `tool.uv.dev-dependencies`.
        let dev_dependencies = self
            .doc
            .entry("tool")
            .or_insert(implicit())
            .as_table_mut()
            .ok_or(Error::MalformedSources)?
            .entry("uv")
            .or_insert(Item::Table(Table::new()))
            .as_table_mut()
            .ok_or(Error::MalformedSources)?
            .entry("dev-dependencies")
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedDependencies)?;

        let Some(req) = dev_dependencies.get(index) else {
            return Err(Error::MissingDependency(index));
        };

        let mut req = req
            .as_str()
            .and_then(try_parse_requirement)
            .ok_or(Error::MalformedDependencies)?;
        req.version_or_url = Some(VersionOrUrl::VersionSpecifier(VersionSpecifiers::from(
            VersionSpecifier::greater_than_equal_version(version),
        )));
        dev_dependencies.replace(index, req.to_string());

        Ok(())
    }

    /// Set the minimum version for an existing dependency in `project.optional-dependencies`.
    pub fn set_optional_dependency_minimum_version(
        &mut self,
        group: &ExtraName,
        index: usize,
        version: Version,
    ) -> Result<(), Error> {
        // Get or create `project.optional-dependencies`.
        let optional_dependencies = self
            .project()?
            .entry("optional-dependencies")
            .or_insert(Item::Table(Table::new()))
            .as_table_like_mut()
            .ok_or(Error::MalformedDependencies)?;

        let group = optional_dependencies
            .entry(group.as_ref())
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedDependencies)?;

        let Some(req) = group.get(index) else {
            return Err(Error::MissingDependency(index));
        };

        let mut req = req
            .as_str()
            .and_then(try_parse_requirement)
            .ok_or(Error::MalformedDependencies)?;
        req.version_or_url = Some(VersionOrUrl::VersionSpecifier(VersionSpecifiers::from(
            VersionSpecifier::greater_than_equal_version(version),
        )));
        group.replace(index, req.to_string());

        Ok(())
    }

    /// Set the minimum version for an existing dependency in `dependency-groups`.
    pub fn set_dependency_group_requirement_minimum_version(
        &mut self,
        group: &GroupName,
        index: usize,
        version: Version,
    ) -> Result<(), Error> {
        // Get or create `dependency-groups`.
        let dependency_groups = self
            .doc
            .entry("dependency-groups")
            .or_insert(Item::Table(Table::new()))
            .as_table_like_mut()
            .ok_or(Error::MalformedDependencies)?;

        let group = dependency_groups
            .entry(group.as_ref())
            .or_insert(Item::Value(Value::Array(Array::new())))
            .as_array_mut()
            .ok_or(Error::MalformedDependencies)?;

        let Some(req) = group.get(index) else {
            return Err(Error::MissingDependency(index));
        };

        let mut req = req
            .as_str()
            .and_then(try_parse_requirement)
            .ok_or(Error::MalformedDependencies)?;
        req.version_or_url = Some(VersionOrUrl::VersionSpecifier(VersionSpecifiers::from(
            VersionSpecifier::greater_than_equal_version(version),
        )));
        group.replace(index, req.to_string());

        Ok(())
    }

    /// Adds a source to `tool.uv.sources`.
    fn add_source(&mut self, name: &PackageName, source: &Source) -> Result<(), Error> {
        // Get or create `tool.uv.sources`.
        let sources = self
            .doc
            .entry("tool")
            .or_insert(implicit())
            .as_table_mut()
            .ok_or(Error::MalformedSources)?
            .entry("uv")
            .or_insert(implicit())
            .as_table_mut()
            .ok_or(Error::MalformedSources)?
            .entry("sources")
            .or_insert(Item::Table(Table::new()))
            .as_table_mut()
            .ok_or(Error::MalformedSources)?;

        if let Some(key) = find_source(name, sources) {
            sources.remove(&key);
        }
        add_source(name, source, sources)?;

        Ok(())
    }

    /// Removes all occurrences of dependencies with the given name.
    pub fn remove_dependency(&mut self, name: &PackageName) -> Result<Vec<Requirement>, Error> {
        // Try to get `project.dependencies`.
        let Some(dependencies) = self
            .project_mut()?
            .and_then(|project| project.get_mut("dependencies"))
            .map(|dependencies| {
                dependencies
                    .as_array_mut()
                    .ok_or(Error::MalformedDependencies)
            })
            .transpose()?
        else {
            return Ok(Vec::new());
        };

        let requirements = remove_dependency(name, dependencies);
        self.remove_source(name)?;

        Ok(requirements)
    }

    /// Removes all occurrences of development dependencies with the given name.
    pub fn remove_dev_dependency(&mut self, name: &PackageName) -> Result<Vec<Requirement>, Error> {
        // Try to get `tool.uv.dev-dependencies`.
        let Some(dev_dependencies) = self
            .doc
            .get_mut("tool")
            .map(|tool| tool.as_table_mut().ok_or(Error::MalformedDependencies))
            .transpose()?
            .and_then(|tool| tool.get_mut("uv"))
            .map(|tool_uv| tool_uv.as_table_mut().ok_or(Error::MalformedDependencies))
            .transpose()?
            .and_then(|tool_uv| tool_uv.get_mut("dev-dependencies"))
            .map(|dependencies| {
                dependencies
                    .as_array_mut()
                    .ok_or(Error::MalformedDependencies)
            })
            .transpose()?
        else {
            return Ok(Vec::new());
        };

        let requirements = remove_dependency(name, dev_dependencies);
        self.remove_source(name)?;

        Ok(requirements)
    }

    /// Removes all occurrences of optional dependencies in the group with the given name.
    pub fn remove_optional_dependency(
        &mut self,
        name: &PackageName,
        group: &ExtraName,
    ) -> Result<Vec<Requirement>, Error> {
        // Try to get `project.optional-dependencies.<group>`.
        let Some(optional_dependencies) = self
            .project_mut()?
            .and_then(|project| project.get_mut("optional-dependencies"))
            .map(|extras| {
                extras
                    .as_table_like_mut()
                    .ok_or(Error::MalformedDependencies)
            })
            .transpose()?
            .and_then(|extras| extras.get_mut(group.as_ref()))
            .map(|dependencies| {
                dependencies
                    .as_array_mut()
                    .ok_or(Error::MalformedDependencies)
            })
            .transpose()?
        else {
            return Ok(Vec::new());
        };

        let requirements = remove_dependency(name, optional_dependencies);
        self.remove_source(name)?;

        Ok(requirements)
    }

    /// Removes all occurrences of the dependency in the group with the given name.
    pub fn remove_dependency_group_requirement(
        &mut self,
        name: &PackageName,
        group: &GroupName,
    ) -> Result<Vec<Requirement>, Error> {
        // Try to get `project.optional-dependencies.<group>`.
        let Some(group_dependencies) = self
            .doc
            .get_mut("dependency-groups")
            .map(|groups| {
                groups
                    .as_table_like_mut()
                    .ok_or(Error::MalformedDependencies)
            })
            .transpose()?
            .and_then(|groups| groups.get_mut(group.as_ref()))
            .map(|dependencies| {
                dependencies
                    .as_array_mut()
                    .ok_or(Error::MalformedDependencies)
            })
            .transpose()?
        else {
            return Ok(Vec::new());
        };

        let requirements = remove_dependency(name, group_dependencies);
        self.remove_source(name)?;

        Ok(requirements)
    }

    /// Remove a matching source from `tool.uv.sources`, if it exists.
    fn remove_source(&mut self, name: &PackageName) -> Result<(), Error> {
        // If the dependency is still in use, don't remove the source.
        if !self.find_dependency(name, None).is_empty() {
            return Ok(());
        }

        if let Some(sources) = self
            .doc
            .get_mut("tool")
            .map(|tool| tool.as_table_mut().ok_or(Error::MalformedSources))
            .transpose()?
            .and_then(|tool| tool.get_mut("uv"))
            .map(|tool_uv| tool_uv.as_table_mut().ok_or(Error::MalformedSources))
            .transpose()?
            .and_then(|tool_uv| tool_uv.get_mut("sources"))
            .map(|sources| sources.as_table_mut().ok_or(Error::MalformedSources))
            .transpose()?
        {
            if let Some(key) = find_source(name, sources) {
                sources.remove(&key);

                // Remove the `tool.uv.sources` table if it is empty.
                if sources.is_empty() {
                    self.doc
                        .entry("tool")
                        .or_insert(implicit())
                        .as_table_mut()
                        .ok_or(Error::MalformedSources)?
                        .entry("uv")
                        .or_insert(implicit())
                        .as_table_mut()
                        .ok_or(Error::MalformedSources)?
                        .remove("sources");
                }
            }
        }

        Ok(())
    }

    /// Returns `true` if the `tool.uv.dev-dependencies` table is present.
    pub fn has_dev_dependencies(&self) -> bool {
        self.doc
            .get("tool")
            .and_then(Item::as_table)
            .and_then(|tool| tool.get("uv"))
            .and_then(Item::as_table)
            .and_then(|uv| uv.get("dev-dependencies"))
            .is_some()
    }

    /// Returns `true` if the `dependency-groups` table is present and contains the given group.
    pub fn has_dependency_group(&self, group: &GroupName) -> bool {
        self.doc
            .get("dependency-groups")
            .and_then(Item::as_table)
            .and_then(|groups| groups.get(group.as_ref()))
            .is_some()
    }

    /// Returns all the places in this `pyproject.toml` that contain a dependency with the given
    /// name.
    ///
    /// This method searches `project.dependencies`, `tool.uv.dev-dependencies`, and
    /// `tool.uv.optional-dependencies`.
    pub fn find_dependency(
        &self,
        name: &PackageName,
        marker: Option<&MarkerTree>,
    ) -> Vec<DependencyType> {
        let mut types = Vec::new();

        if let Some(project) = self.doc.get("project").and_then(Item::as_table) {
            // Check `project.dependencies`.
            if let Some(dependencies) = project.get("dependencies").and_then(Item::as_array) {
                if !find_dependencies(name, marker, dependencies).is_empty() {
                    types.push(DependencyType::Production);
                }
            }

            // Check `project.optional-dependencies`.
            if let Some(extras) = project
                .get("optional-dependencies")
                .and_then(Item::as_table)
            {
                for (extra, dependencies) in extras {
                    let Some(dependencies) = dependencies.as_array() else {
                        continue;
                    };
                    let Ok(extra) = ExtraName::new(extra.to_string()) else {
                        continue;
                    };

                    if !find_dependencies(name, marker, dependencies).is_empty() {
                        types.push(DependencyType::Optional(extra));
                    }
                }
            }
        }

        // Check `dependency-groups`.
        if let Some(groups) = self.doc.get("dependency-groups").and_then(Item::as_table) {
            for (group, dependencies) in groups {
                let Some(dependencies) = dependencies.as_array() else {
                    continue;
                };
                let Ok(group) = GroupName::new(group.to_string()) else {
                    continue;
                };

                if !find_dependencies(name, marker, dependencies).is_empty() {
                    types.push(DependencyType::Group(group));
                }
            }
        }

        // Check `tool.uv.dev-dependencies`.
        if let Some(dev_dependencies) = self
            .doc
            .get("tool")
            .and_then(Item::as_table)
            .and_then(|tool| tool.get("uv"))
            .and_then(Item::as_table)
            .and_then(|uv| uv.get("dev-dependencies"))
            .and_then(Item::as_array)
        {
            if !find_dependencies(name, marker, dev_dependencies).is_empty() {
                types.push(DependencyType::Dev);
            }
        }

        types
    }
}

/// Returns an implicit table.
fn implicit() -> Item {
    let mut table = Table::new();
    table.set_implicit(true);
    Item::Table(table)
}

/// Adds a dependency to the given `deps` array.
///
/// Returns `true` if the dependency was added, `false` if it was updated.
pub fn add_dependency(
    req: &Requirement,
    deps: &mut Array,
    has_source: bool,
) -> Result<ArrayEdit, Error> {
    let mut to_replace = find_dependencies(&req.name, Some(&req.marker), deps);

    match to_replace.as_slice() {
        [] => {
            #[derive(Debug, Copy, Clone)]
            enum Sort {
                /// The list is sorted in a case-sensitive manner.
                CaseSensitive,
                /// The list is sorted in a case-insensitive manner.
                CaseInsensitive,
                /// The list is unsorted.
                Unsorted,
            }

            // Determine if the dependency list is sorted prior to
            // adding the new dependency; the new dependency list
            // will be sorted only when the original list is sorted
            // so that user's custom dependency ordering is preserved.
            //
            // Additionally, if the table is invalid (i.e. contains non-string values)
            // we still treat it as unsorted for the sake of simplicity.
            //
            // We account for both case-sensitive and case-insensitive sorting.
            let sort = deps
                .iter()
                .all(Value::is_str)
                .then(|| {
                    if deps.iter().tuple_windows().all(|(a, b)| {
                        a.as_str()
                            .map(str::to_lowercase)
                            .as_deref()
                            .map(split_specifiers)
                            <= b.as_str()
                                .map(str::to_lowercase)
                                .as_deref()
                                .map(split_specifiers)
                    }) {
                        Some(Sort::CaseInsensitive)
                    } else if deps.iter().tuple_windows().all(|(a, b)| {
                        a.as_str().map(split_specifiers) <= b.as_str().map(split_specifiers)
                    }) {
                        Some(Sort::CaseSensitive)
                    } else {
                        None
                    }
                })
                .flatten()
                .unwrap_or(Sort::Unsorted);

            let req_string = req.to_string();
            let index = match sort {
                Sort::CaseSensitive => deps
                    .iter()
                    .position(|d| d.as_str() > Some(req_string.as_str())),
                Sort::CaseInsensitive => deps.iter().position(|d| {
                    d.as_str().map(str::to_lowercase) > Some(req_string.as_str().to_lowercase())
                }),
                Sort::Unsorted => None,
            };
            let index = index.unwrap_or(deps.len());

            let mut value = Value::from(req_string.as_str());

            let decor = value.decor_mut();

            // If we're adding to the end of the list, treat trailing comments as leading comments
            // on the added dependency.
            //
            // For example, given:
            // ```toml
            // dependencies = [
            //     "anyio", # trailing comment
            // ]
            // ```
            //
            // If we add `flask` to the end, we want to retain the comment on `anyio`:
            // ```toml
            // dependencies = [
            //     "anyio", # trailing comment
            //     "flask",
            // ]
            // ```
            if index == deps.len() {
                decor.set_prefix(deps.trailing().clone());
                deps.set_trailing("");
            }

            deps.insert_formatted(index, value);

            // `reformat_array_multiline` uses the indentation of the first dependency entry.
            // Therefore, we retrieve the indentation of the first dependency entry and apply it to
            // the new entry. Note that it is only necessary if the newly added dependency is going
            // to be the first in the list _and_ the dependency list was not empty prior to adding
            // the new dependency.
            if deps.len() > 1 && index == 0 {
                let prefix = deps
                    .clone()
                    .get(index + 1)
                    .unwrap()
                    .decor()
                    .prefix()
                    .unwrap()
                    .clone();

                // However, if the prefix includes a comment, we don't want to duplicate it.
                // Depending on the location of the comment, we either want to leave it as-is, or
                // attach it to the entry that's being moved to the next line.
                //
                // For example, given:
                // ```toml
                // dependencies = [ # comment
                //     "flask",
                // ]
                // ```
                //
                // If we add `anyio` to the beginning, we want to retain the comment on the open
                // bracket:
                // ```toml
                // dependencies = [ # comment
                //     "anyio",
                //     "flask",
                // ]
                // ```
                //
                // However, given:
                // ```toml
                // dependencies = [
                //     # comment
                //     "flask",
                // ]
                // ```
                //
                // If we add `anyio` to the beginning, we want the comment to move down with the
                // existing entry:
                // entry:
                // ```toml
                // dependencies = [
                //     "anyio",
                //     # comment
                //     "flask",
                // ]
                if let Some(prefix) = prefix.as_str() {
                    // Treat anything before the first own-line comment as a prefix on the new
                    // entry; anything after the first own-line comment is a prefix on the existing
                    // entry.
                    //
                    // This is equivalent to using the first and last line content as the prefix for
                    // the new entry, and the rest as the prefix for the existing entry.
                    if let Some((first_line, rest)) = prefix.split_once(['\r', '\n']) {
                        // Determine the appropriate newline character.
                        let newline = {
                            let mut chars = prefix[first_line.len()..].chars();
                            match (chars.next(), chars.next()) {
                                (Some('\r'), Some('\n')) => "\r\n",
                                (Some('\r'), _) => "\r",
                                (Some('\n'), _) => "\n",
                                _ => "\n",
                            }
                        };
                        let last_line = rest.lines().last().unwrap_or_default();
                        let prefix = format!("{first_line}{newline}{last_line}");
                        deps.get_mut(index).unwrap().decor_mut().set_prefix(prefix);

                        let prefix = format!("{newline}{rest}");
                        deps.get_mut(index + 1)
                            .unwrap()
                            .decor_mut()
                            .set_prefix(prefix);
                    } else {
                        deps.get_mut(index).unwrap().decor_mut().set_prefix(prefix);
                    }
                } else {
                    deps.get_mut(index).unwrap().decor_mut().set_prefix(prefix);
                }
            }

            reformat_array_multiline(deps);

            Ok(ArrayEdit::Add(index))
        }
        [_] => {
            let (i, mut old_req) = to_replace.remove(0);
            update_requirement(&mut old_req, req, has_source);
            deps.replace(i, old_req.to_string());
            reformat_array_multiline(deps);
            Ok(ArrayEdit::Update(i))
        }
        // Cannot perform ambiguous updates.
        _ => Err(Error::Ambiguous),
    }
}

/// Update an existing requirement.
fn update_requirement(old: &mut Requirement, new: &Requirement, has_source: bool) {
    // Add any new extras.
    old.extras.extend(new.extras.iter().cloned());
    old.extras.sort_unstable();
    old.extras.dedup();

    // Clear the requirement source if we are going to add to `tool.uv.sources`.
    if has_source {
        old.clear_url();
    }

    // Update the source if a new one was specified.
    match &new.version_or_url {
        None => {}
        Some(VersionOrUrl::VersionSpecifier(specifier)) if specifier.is_empty() => {}
        Some(version_or_url) => old.version_or_url = Some(version_or_url.clone()),
    }

    // Update the marker expression.
    if new.marker.contents().is_some() {
        old.marker = new.marker.clone();
    }
}

/// Removes all occurrences of dependencies with the given name from the given `deps` array.
fn remove_dependency(name: &PackageName, deps: &mut Array) -> Vec<Requirement> {
    // Remove matching dependencies.
    let removed = find_dependencies(name, None, deps)
        .into_iter()
        .rev() // Reverse to preserve indices as we remove them.
        .filter_map(|(i, _)| {
            deps.remove(i)
                .as_str()
                .and_then(|req| Requirement::from_str(req).ok())
        })
        .collect::<Vec<_>>();

    if !removed.is_empty() {
        reformat_array_multiline(deps);
    }

    removed
}

/// Returns a `Vec` containing the all dependencies with the given name, along with their positions
/// in the array.
fn find_dependencies(
    name: &PackageName,
    marker: Option<&MarkerTree>,
    deps: &Array,
) -> Vec<(usize, Requirement)> {
    let mut to_replace = Vec::new();
    for (i, dep) in deps.iter().enumerate() {
        if let Some(req) = dep.as_str().and_then(try_parse_requirement) {
            if marker.map_or(true, |m| *m == req.marker) && *name == req.name {
                to_replace.push((i, req));
            }
        }
    }
    to_replace
}

/// Returns the key in `tool.uv.sources` that matches the given package name.
fn find_source(name: &PackageName, sources: &Table) -> Option<String> {
    for (key, _) in sources {
        if PackageName::from_str(key).is_ok_and(|ref key| key == name) {
            return Some(key.to_string());
        }
    }
    None
}

// Add a source to `tool.uv.sources`.
fn add_source(req: &PackageName, source: &Source, sources: &mut Table) -> Result<(), Error> {
    // Serialize as an inline table.
    let mut doc = toml::to_string(&source)
        .map_err(Box::new)?
        .parse::<DocumentMut>()
        .unwrap();
    let table = mem::take(doc.as_table_mut()).into_inline_table();

    sources.insert(req.as_ref(), Item::Value(Value::InlineTable(table)));

    Ok(())
}

impl fmt::Display for PyProjectTomlMut {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.doc.fmt(f)
    }
}

fn try_parse_requirement(req: &str) -> Option<Requirement> {
    Requirement::from_str(req).ok()
}

/// Reformats a TOML array to multi line while trying to preserve all comments
/// and move them around. This also formats the array to have a trailing comma.
fn reformat_array_multiline(deps: &mut Array) {
    fn find_comments(s: Option<&RawString>) -> Box<dyn Iterator<Item = Comment> + '_> {
        let iter = s
            .and_then(|x| x.as_str())
            .unwrap_or("")
            .lines()
            .scan(
                (false, false),
                |(prev_line_was_empty, prev_line_was_comment), line| {
                    let trimmed_line = line.trim();
                    if let Some(index) = trimmed_line.find('#') {
                        let comment_text = trimmed_line[index..].trim().to_string();
                        let comment_type = if (*prev_line_was_empty) || (*prev_line_was_comment) {
                            CommentType::OwnLine
                        } else {
                            CommentType::EndOfLine
                        };
                        *prev_line_was_empty = trimmed_line.is_empty();
                        *prev_line_was_comment = true;
                        Some(Some(Comment {
                            text: comment_text,
                            comment_type,
                        }))
                    } else {
                        *prev_line_was_empty = trimmed_line.is_empty();
                        *prev_line_was_comment = false;
                        Some(None)
                    }
                },
            )
            .flatten();

        Box::new(iter)
    }

    let mut indentation_prefix = None;

    for item in deps.iter_mut() {
        let decor = item.decor_mut();
        let mut prefix = String::new();

        // Calculate the indentation prefix based on the indentation of the first dependency entry.
        if indentation_prefix.is_none() {
            let decor_prefix = decor
                .prefix()
                .and_then(|s| s.as_str())
                .and_then(|s| s.lines().last())
                .unwrap_or_default();

            let decor_prefix = decor_prefix
                .split_once('#')
                .map(|(s, _)| s)
                .unwrap_or(decor_prefix);

            // If there is no indentation, use four-space.
            indentation_prefix = Some(if decor_prefix.is_empty() {
                "    ".to_string()
            } else {
                decor_prefix.to_string()
            });
        }

        let indentation_prefix_str = format!("\n{}", indentation_prefix.as_ref().unwrap());

        for comment in find_comments(decor.prefix()).chain(find_comments(decor.suffix())) {
            match comment.comment_type {
                CommentType::OwnLine => {
                    prefix.push_str(&indentation_prefix_str);
                }
                CommentType::EndOfLine => {
                    prefix.push(' ');
                }
            }
            prefix.push_str(&comment.text);
        }
        prefix.push_str(&indentation_prefix_str);
        decor.set_prefix(prefix);
        decor.set_suffix("");
    }

    deps.set_trailing(&{
        let mut comments = find_comments(Some(deps.trailing())).peekable();
        let mut rv = String::new();
        if comments.peek().is_some() {
            for comment in comments {
                match comment.comment_type {
                    CommentType::OwnLine => {
                        let indentation_prefix_str =
                            format!("\n{}", indentation_prefix.as_ref().unwrap());
                        rv.push_str(&indentation_prefix_str);
                    }
                    CommentType::EndOfLine => {
                        rv.push(' ');
                    }
                }
                rv.push_str(&comment.text);
            }
        }
        if !rv.is_empty() || !deps.is_empty() {
            rv.push('\n');
        }
        rv
    });
    deps.set_trailing_comma(true);
}

/// Split a requirement into the package name and its dependency specifiers.
///
/// E.g., given `flask>=1.0`, this function returns `("flask", ">=1.0")`. But given
/// `Flask>=1.0`, this function returns `("Flask", ">=1.0")`.
///
/// Extras are retained, such that `flask[dotenv]>=1.0` returns `("flask[dotenv]", ">=1.0")`.
fn split_specifiers(req: &str) -> (&str, &str) {
    let (name, specifiers) = req
        .find(['>', '<', '=', '~', '!', '@'])
        .map_or((req, ""), |pos| {
            let (name, specifiers) = req.split_at(pos);
            (name, specifiers)
        });
    (name.trim(), specifiers.trim())
}

#[cfg(test)]
mod test {
    use super::split_specifiers;

    #[test]
    fn split() {
        assert_eq!(split_specifiers("flask>=1.0"), ("flask", ">=1.0"));
        assert_eq!(split_specifiers("Flask>=1.0"), ("Flask", ">=1.0"));
        assert_eq!(
            split_specifiers("flask[dotenv]>=1.0"),
            ("flask[dotenv]", ">=1.0")
        );
        assert_eq!(split_specifiers("flask[dotenv]",), ("flask[dotenv]", ""));
        assert_eq!(split_specifiers("flask @ https://files.pythonhosted.org/packages/af/47/93213ee66ef8fae3b93b3e29206f6b251e65c97bd91d8e1c5596ef15af0a/flask-3.1.0-py3-none-any.whl"), ("flask", "@ https://files.pythonhosted.org/packages/af/47/93213ee66ef8fae3b93b3e29206f6b251e65c97bd91d8e1c5596ef15af0a/flask-3.1.0-py3-none-any.whl"));
    }
}
