use nu_engine::{eval_block, CallExt};
use nu_protocol::ast::Call;
use nu_protocol::engine::{Closure, Command, EngineState, Stack};
use nu_protocol::{
    Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, ShellError,
    Signature, Span, SyntaxShape, Type, Value,
};

#[derive(Clone)]
pub struct Where;

impl Command for Where {
    fn name(&self) -> &str {
        "where"
    }

    fn usage(&self) -> &str {
        "Filter values based on a row condition."
    }

    fn extra_usage(&self) -> &str {
        r#"This command works similar to 'filter' but allows extra shorthands for working with
tables, known as "row conditions". On the other hand, reading the condition from a variable is
not supported."#
    }

    fn signature(&self) -> nu_protocol::Signature {
        Signature::build("where")
            .input_output_types(vec![
                (
                    Type::List(Box::new(Type::Any)),
                    Type::List(Box::new(Type::Any)),
                ),
                (Type::Table(vec![]), Type::Table(vec![])),
            ])
            .required(
                "row_condition",
                SyntaxShape::RowCondition,
                "Filter condition",
            )
            .category(Category::Filters)
    }

    fn search_terms(&self) -> Vec<&str> {
        vec!["filter", "find", "search", "condition"]
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let closure: Closure = call.req(engine_state, stack, 0)?;

        let span = call.head;

        let metadata = input.metadata();
        let mut stack = stack.captures_to_stack(&closure.captures);
        let block = engine_state.get_block(closure.block_id).clone();

        let orig_env_vars = stack.env_vars.clone();
        let orig_env_hidden = stack.env_hidden.clone();

        let ctrlc = engine_state.ctrlc.clone();
        let engine_state = engine_state.clone();

        let redirect_stdout = call.redirect_stdout;
        let redirect_stderr = call.redirect_stderr;
        Ok(input
            .into_iter_strict(span)?
            .filter_map(move |value| {
                stack.with_env(&orig_env_vars, &orig_env_hidden);

                if let Some(var) = block.signature.get_positional(0) {
                    if let Some(var_id) = &var.var_id {
                        stack.add_var(*var_id, value.clone());
                    }
                }
                let result = eval_block(
                    &engine_state,
                    &mut stack,
                    &block,
                    // clone() is used here because x is given to Ok() below.
                    value.clone().into_pipeline_data(),
                    redirect_stdout,
                    redirect_stderr,
                );

                match result {
                    Ok(result) => {
                        let result = result.into_value(span);
                        if result.is_true() {
                            Some(value)
                        } else {
                            None
                        }
                    }
                    Err(err) => Some(Value::Error {
                        error: Box::new(err),
                    }),
                }
            })
            .into_pipeline_data(ctrlc)
            .set_metadata(metadata))
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Filter rows of a table according to a condition",
                example: "[{a: 1} {a: 2}] | where a > 1",
                result: Some(Value::List {
                    vals: vec![Value::Record {
                        cols: vec!["a".to_string()],
                        vals: vec![Value::test_int(2)],
                        span: Span::test_data(),
                    }],
                    span: Span::test_data(),
                }),
            },
            Example {
                description: "Filter items of a list according to a condition",
                example: "[1 2] | where {|x| $x > 1}",
                result: Some(Value::List {
                    vals: vec![Value::test_int(2)],
                    span: Span::test_data(),
                }),
            },
            Example {
                description: "List all files in the current directory with sizes greater than 2kb",
                example: "ls | where size > 2kb",
                result: None,
            },
            Example {
                description: "List only the files in the current directory",
                example: "ls | where type == file",
                result: None,
            },
            Example {
                description: "List all files with names that contain \"Car\"",
                example: "ls | where name =~ \"Car\"",
                result: None,
            },
            Example {
                description: "List all files that were modified in the last two weeks",
                example: "ls | where modified >= (date now) - 2wk",
                result: None,
            },
            Example {
                description: "Find files whose filenames don't begin with the correct sequential number",
                example: "ls | where type == file | sort-by name -n | enumerate | where {|e| $e.item.name !~ $'^($e.index + 1)' } | each {|| get item }",
                result: None,
            },
        ]
    }
}

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

    #[test]
    fn test_examples() {
        use crate::test_examples;

        test_examples(Where {})
    }
}
