use log::trace;
use nu_engine::eval_block;
use nu_parser::{escape_quote_string, lex, parse, unescape_unquote_string, Token, TokenContents};
use nu_protocol::engine::StateWorkingSet;
use nu_protocol::CliError;
use nu_protocol::{
    engine::{EngineState, Stack},
    PipelineData, ShellError, Span, Value,
};
#[cfg(windows)]
use nu_utils::enable_vt_processing;
use std::path::{Path, PathBuf};

// This will collect environment variables from std::env and adds them to a stack.
//
// In order to ensure the values have spans, it first creates a dummy file, writes the collected
// env vars into it (in a "NAME"="value" format, quite similar to the output of the Unix 'env'
// tool), then uses the file to get the spans. The file stays in memory, no filesystem IO is done.
//
// The "PWD" env value will be forced to `init_cwd`.
// The reason to use `init_cwd`:
//
// While gathering parent env vars, the parent `PWD` may not be the same as `current working directory`.
// Consider to the following command as the case (assume we execute command inside `/tmp`):
//
//     tmux split-window -v -c "#{pane_current_path}"
//
// Here nu execute external command `tmux`, and tmux starts a new `nushell`, with `init_cwd` value "#{pane_current_path}".
// But at the same time `PWD` still remains to be `/tmp`.
//
// In this scenario, the new `nushell`'s PWD should be "#{pane_current_path}" rather init_cwd.
pub fn gather_parent_env_vars(engine_state: &mut EngineState, init_cwd: &Path) {
    gather_env_vars(std::env::vars(), engine_state, init_cwd);
}

fn gather_env_vars(
    vars: impl Iterator<Item = (String, String)>,
    engine_state: &mut EngineState,
    init_cwd: &Path,
) {
    fn report_capture_error(engine_state: &EngineState, env_str: &str, msg: &str) {
        let working_set = StateWorkingSet::new(engine_state);
        report_error(
            &working_set,
            &ShellError::GenericError(
                format!("Environment variable was not captured: {}", env_str),
                "".to_string(),
                None,
                Some(msg.into()),
                Vec::new(),
            ),
        );
    }

    fn put_env_to_fake_file(name: &str, val: &str, fake_env_file: &mut String) {
        fake_env_file.push_str(&escape_quote_string(name));
        fake_env_file.push('=');
        fake_env_file.push_str(&escape_quote_string(val));
        fake_env_file.push('\n');
    }

    let mut fake_env_file = String::new();
    // Write all the env vars into a fake file
    for (name, val) in vars {
        put_env_to_fake_file(&name, &val, &mut fake_env_file);
    }

    match init_cwd.to_str() {
        Some(cwd) => {
            put_env_to_fake_file("PWD", cwd, &mut fake_env_file);
        }
        None => {
            // Could not capture current working directory
            let working_set = StateWorkingSet::new(engine_state);
            report_error(
                &working_set,
                &ShellError::GenericError(
                    "Current directory is not a valid utf-8 path".to_string(),
                    "".to_string(),
                    None,
                    Some(format!(
                        "Retrieving current directory failed: {:?} not a valid utf-8 path",
                        init_cwd
                    )),
                    Vec::new(),
                ),
            );
        }
    }

    // Lex the fake file, assign spans to all environment variables and add them
    // to stack
    let span_offset = engine_state.next_span_start();

    engine_state.add_file(
        "Host Environment Variables".to_string(),
        fake_env_file.as_bytes().to_vec(),
    );

    let (tokens, _) = lex(fake_env_file.as_bytes(), span_offset, &[], &[], true);

    for token in tokens {
        if let Token {
            contents: TokenContents::Item,
            span: full_span,
        } = token
        {
            let contents = engine_state.get_span_contents(&full_span);
            let (parts, _) = lex(contents, full_span.start, &[], &[b'='], true);

            let name = if let Some(Token {
                contents: TokenContents::Item,
                span,
            }) = parts.get(0)
            {
                let bytes = engine_state.get_span_contents(span);

                if bytes.len() < 2 {
                    report_capture_error(
                        engine_state,
                        &String::from_utf8_lossy(contents),
                        "Got empty name.",
                    );

                    continue;
                }

                let (bytes, parse_error) = unescape_unquote_string(bytes, *span);

                if parse_error.is_some() {
                    report_capture_error(
                        engine_state,
                        &String::from_utf8_lossy(contents),
                        "Got unparsable name.",
                    );

                    continue;
                }

                bytes
            } else {
                report_capture_error(
                    engine_state,
                    &String::from_utf8_lossy(contents),
                    "Got empty name.",
                );

                continue;
            };

            let value = if let Some(Token {
                contents: TokenContents::Item,
                span,
            }) = parts.get(2)
            {
                let bytes = engine_state.get_span_contents(span);

                if bytes.len() < 2 {
                    report_capture_error(
                        engine_state,
                        &String::from_utf8_lossy(contents),
                        "Got empty value.",
                    );

                    continue;
                }

                let (bytes, parse_error) = unescape_unquote_string(bytes, *span);

                if parse_error.is_some() {
                    report_capture_error(
                        engine_state,
                        &String::from_utf8_lossy(contents),
                        "Got unparsable value.",
                    );

                    continue;
                }

                Value::String {
                    val: bytes,
                    span: *span,
                }
            } else {
                report_capture_error(
                    engine_state,
                    &String::from_utf8_lossy(contents),
                    "Got empty value.",
                );

                continue;
            };

            // stack.add_env_var(name, value);
            engine_state.add_env_var(name, value);
        }
    }
}

pub fn eval_source(
    engine_state: &mut EngineState,
    stack: &mut Stack,
    source: &[u8],
    fname: &str,
    input: PipelineData,
) -> bool {
    trace!("eval_source");

    let (block, delta) = {
        let mut working_set = StateWorkingSet::new(engine_state);
        let (output, err) = parse(
            &mut working_set,
            Some(fname), // format!("entry #{}", entry_num)
            source,
            false,
            &[],
        );
        if let Some(err) = err {
            set_last_exit_code(stack, 1);
            report_error(&working_set, &err);
            return false;
        }

        (output, working_set.render())
    };

    if let Err(err) = engine_state.merge_delta(delta) {
        set_last_exit_code(stack, 1);
        report_error_new(engine_state, &err);
        return false;
    }

    match eval_block(engine_state, stack, &block, input, false, false) {
        Ok(mut pipeline_data) => {
            if let PipelineData::ExternalStream { exit_code, .. } = &mut pipeline_data {
                if let Some(exit_code) = exit_code.take().and_then(|it| it.last()) {
                    stack.add_env_var("LAST_EXIT_CODE".to_string(), exit_code);
                } else {
                    set_last_exit_code(stack, 0);
                }
            } else {
                set_last_exit_code(stack, 0);
            }

            if let Err(err) = pipeline_data.print(engine_state, stack, false, false) {
                let working_set = StateWorkingSet::new(engine_state);

                report_error(&working_set, &err);

                return false;
            }

            // reset vt processing, aka ansi because illbehaved externals can break it
            #[cfg(windows)]
            {
                let _ = enable_vt_processing();
            }
        }
        Err(err) => {
            set_last_exit_code(stack, 1);

            let working_set = StateWorkingSet::new(engine_state);

            report_error(&working_set, &err);

            return false;
        }
    }

    true
}

fn set_last_exit_code(stack: &mut Stack, exit_code: i64) {
    stack.add_env_var(
        "LAST_EXIT_CODE".to_string(),
        Value::Int {
            val: exit_code,
            span: Span { start: 0, end: 0 },
        },
    );
}

pub fn report_error(
    working_set: &StateWorkingSet,
    error: &(dyn miette::Diagnostic + Send + Sync + 'static),
) {
    eprintln!("Error: {:?}", CliError(error, working_set));
    // reset vt processing, aka ansi because illbehaved externals can break it
    #[cfg(windows)]
    {
        let _ = nu_utils::enable_vt_processing();
    }
}

pub fn report_error_new(
    engine_state: &EngineState,
    error: &(dyn miette::Diagnostic + Send + Sync + 'static),
) {
    let working_set = StateWorkingSet::new(engine_state);

    report_error(&working_set, error);
}

pub fn get_init_cwd() -> PathBuf {
    match std::env::current_dir() {
        Ok(cwd) => cwd,
        Err(_) => match std::env::var("PWD") {
            Ok(cwd) => PathBuf::from(cwd),
            Err(_) => match nu_path::home_dir() {
                Some(cwd) => cwd,
                None => PathBuf::new(),
            },
        },
    }
}

pub fn get_guaranteed_cwd(engine_state: &EngineState, stack: &Stack) -> PathBuf {
    match nu_engine::env::current_dir(engine_state, stack) {
        Ok(p) => p,
        Err(e) => {
            let working_set = StateWorkingSet::new(engine_state);
            report_error(&working_set, &e);
            get_init_cwd()
        }
    }
}

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

    #[test]
    fn test_gather_env_vars() {
        let mut engine_state = EngineState::new();
        let symbols = r##" !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~"##;

        gather_env_vars(
            [
                ("FOO".into(), "foo".into()),
                ("SYMBOLS".into(), symbols.into()),
                (symbols.into(), "symbols".into()),
            ]
            .into_iter(),
            &mut engine_state,
            Path::new("t"),
        );

        let env = engine_state.render_env_vars();

        assert!(
            matches!(env.get(&"FOO".to_string()), Some(&Value::String { val, .. }) if val == "foo")
        );
        assert!(
            matches!(env.get(&"SYMBOLS".to_string()), Some(&Value::String { val, .. }) if val == symbols)
        );
        assert!(
            matches!(env.get(&symbols.to_string()), Some(&Value::String { val, .. }) if val == "symbols")
        );
        assert!(env.get(&"PWD".to_string()).is_some());
        assert_eq!(env.len(), 4);
    }
}
