use itertools::Itertools as _;
use std::{collections::HashMap, io::Write, str::FromStr as _, sync::Arc};
use strum::IntoEnumIterator;
use tokio::sync::Mutex;

use brush_core::{
    ExecutionExitCode, ExecutionResult, builtins,
    interfaces::{self, InputFunction, KeyAction, KeySequence},
    sys, trace_categories,
};

impl BindKeyMap {
    const fn is_vi(&self) -> bool {
        matches!(self, Self::ViCommand | Self::ViInsert)
    }

    #[expect(dead_code)]
    const fn is_emacs(&self) -> bool {
        matches!(
            self,
            Self::EmacsStandard | Self::EmacsMeta | Self::EmacsCtlx
        )
    }
}

/// Inspect and modify key bindings and other input configuration.
#[derive(winnow_args::Args)]
#[arg(disable_help_short, disable_version_flag, disable_help_subcommand)]
pub(crate) struct BindCommand {
    /// Name of key map to use.
    #[arg(short = 'm')]
    keymap: Option<BindKeyMap>,
    /// List functions.
    #[arg(short = 'l')]
    list_funcs: bool,
    /// List functions and bindings.
    #[arg(short = 'P')]
    list_funcs_and_bindings: bool,
    /// List functions and bindings in a format suitable for use as input.
    #[arg(short = 'p')]
    list_funcs_and_bindings_reusable: bool,
    /// List key sequences that invoke macros.
    #[arg(short = 'S')]
    list_key_seqs_that_invoke_macros: bool,
    /// List key sequences that invoke macros in a format suitable for use as input.
    #[arg(short = 's')]
    list_key_seqs_that_invoke_macros_reusable: bool,
    /// List variables.
    #[arg(short = 'V')]
    list_vars: bool,
    /// List variables in a format suitable for use as input.
    #[arg(short = 'v')]
    list_vars_reusable: bool,
    /// Find the keys bound to the given named function.
    #[arg(short = 'q', value_name = "FUNC_NAME")]
    query_func_bindings: Option<String>,
    /// Remove all bindings for the given named function.
    #[arg(short = 'u', value_name = "FUNC_NAME")]
    remove_func_bindings: Option<String>,
    /// Remove the binding for the given key sequence.
    #[arg(short = 'r', value_name = "KEY_SEQ")]
    remove_key_seq_binding: Option<String>,
    /// Import bindings from the given file.
    #[arg(short = 'f', value_name = "PATH")]
    bindings_file: Option<String>,
    /// Bind key sequence to command.
    #[arg(short = 'x', value_name = "BINDING")]
    key_seq_bindings: Vec<String>,
    /// List key sequence bindings.
    #[arg(short = 'X')]
    list_key_seq_bindings: bool,
    /// Key sequence binding to readline function or command.
    #[arg(positional)]
    key_sequence: Option<String>,
}

/// Identifier for a keymap
#[derive(Clone, winnow_args::ValueEnum)]
pub(crate) enum BindKeyMap {
    #[arg(name = "emacs-standard", alias = "emacs")]
    EmacsStandard,
    #[arg(name = "emacs-meta")]
    EmacsMeta,
    #[arg(name = "emacs-ctlx")]
    EmacsCtlx,
    #[arg(name = "vi-command", alias("vi", "vi-move"))]
    ViCommand,
    #[arg(name = "vi-insert")]
    ViInsert,
}

brush_winnow_args_adapter::impl_parse_args!(BindCommand);

#[derive(Debug, thiserror::Error)]
pub(crate) enum BindError {
    /// Unknown function specified.
    #[error("unknown function: {0}")]
    UnknownFunction(String),

    /// Unknown key binding function.
    #[error("unknown key binding function: {0}")]
    UnknownKeyBindingFunction(String),

    /// Unimplemented functionality.
    #[error("unimplemented: {0}")]
    Unimplemented(&'static str),

    /// An I/O error occurred.
    #[error("I/O error occurred")]
    IoError(#[from] std::io::Error),

    /// A binding parse error occurred.
    #[error(transparent)]
    BindingParseError(#[from] brush_parser::BindingParseError),
}

impl brush_core::BuiltinError for BindError {}

impl From<&BindError> for brush_core::ExecutionExitCode {
    fn from(_err: &BindError) -> Self {
        Self::GeneralError
    }
}

impl<SE: brush_core::ShellExtensions> builtins::Builtin<SE> for BindCommand {
    type Error = BindError;

    async fn execute(
        self,
        context: brush_core::ExecutionContext<'_, SE>,
    ) -> Result<brush_core::ExecutionResult, Self::Error> {
        if let Some(key_bindings) = context.shell.key_bindings() {
            Ok(self.execute_impl(key_bindings, &context).await?)
        } else {
            tracing::debug!(target: trace_categories::INPUT,
                 "bind: key bindings not supported in this config");

            // Silently succeed when key bindings are unavailable (e.g., in
            // non-interactive mode or with an input backend that doesn't
            // yet support them).
            Ok(ExecutionExitCode::Success.into())
        }
    }
}

impl BindCommand {
    #[allow(clippy::too_many_lines)]
    async fn execute_impl(
        &self,
        bindings: &Arc<Mutex<dyn interfaces::KeyBindings>>,
        context: &brush_core::ExecutionContext<'_, impl brush_core::ShellExtensions>,
    ) -> Result<ExecutionResult, BindError> {
        let mut bindings = bindings.lock().await;

        if self.list_funcs {
            for func in interfaces::InputFunction::iter() {
                writeln!(context.stdout(), "{func}")?;
            }
        }

        if self.list_funcs_and_bindings {
            display_funcs_and_bindings(&*bindings, context, false /* reusable? */)?;
        }

        if self.list_funcs_and_bindings_reusable {
            display_funcs_and_bindings(&*bindings, context, true /* reusable? */)?;
        }

        if self.list_key_seqs_that_invoke_macros {
            display_macros(&*bindings, context, false /* reusable? */)?;
        }

        if self.list_key_seqs_that_invoke_macros_reusable {
            display_macros(&*bindings, context, true /* reusable? */)?;
        }

        if self.list_vars {
            let options = &context.shell.completion_config().fallback_options;

            // For now we'll just display a few items and show defaults.
            writeln!(
                context.stdout(),
                "mark-directories is set to `{}'",
                to_onoff(options.mark_directories)
            )?;
            writeln!(
                context.stdout(),
                "mark-symlinked-directories is set to `{}'",
                to_onoff(options.mark_symlinked_directories)
            )?;
        }

        if self.list_vars_reusable {
            let options = &context.shell.completion_config().fallback_options;

            // For now we'll just display a few items and show defaults.
            writeln!(
                context.stdout(),
                "set mark-directories {}",
                to_onoff(options.mark_directories)
            )?;
            writeln!(
                context.stdout(),
                "set mark-symlinked-directories {}",
                to_onoff(options.mark_symlinked_directories)
            )?;
        }

        if let Some(func_str) = &self.query_func_bindings {
            let seqs = find_key_seqs_bound_to_function(&*bindings, func_str)?;

            if !seqs.is_empty() {
                writeln!(
                    context.stdout(),
                    "{func_str} can be invoked via {}.",
                    seqs.iter().map(|seq| std::format!("\"{seq}\"")).join(", ")
                )?;
            } else {
                writeln!(context.stdout(), "{func_str} is not bound to any keys.")?;
                return Ok(ExecutionResult::general_error());
            }
        }

        if let Some(func_str) = &self.remove_func_bindings {
            let found_seqs = find_key_seqs_bound_to_function(&*bindings, func_str)?;

            for seq in found_seqs {
                let _ = bindings.try_unbind(seq);
            }
        }

        if let Some(key_seq_str) = &self.remove_key_seq_binding {
            let key_seq = parse_key_sequence(key_seq_str)?;
            let _ = bindings.try_unbind(key_seq);
        }

        if self.bindings_file.is_some() {
            return Err(BindError::Unimplemented("bind -f"));
        }

        if self.list_key_seq_bindings {
            for (seq, action) in &bindings.get_current() {
                let KeyAction::ShellCommand(cmd) = action else {
                    continue;
                };

                writeln!(context.stdout(), "\"{seq}\" \"{cmd}\"")?;
            }
        }

        if !self.key_seq_bindings.is_empty() {
            if self.keymap.as_ref().is_some_and(|k| k.is_vi()) {
                // NOTE(vi): Quietly ignore since we don't support vi mode.
                return Ok(ExecutionResult::success());
            }

            for key_seq_and_command in &self.key_seq_bindings {
                let (key_seq, command) = parse_key_sequence_and_shell_command(key_seq_and_command)?;
                bind_key_sequence_to_shell_cmd(&mut *bindings, key_seq, command)?;
            }
        }

        if let Some(key_sequence) = &self.key_sequence {
            if self.keymap.as_ref().is_some_and(|k| k.is_vi()) {
                // NOTE(vi): Quietly ignore since we don't support vi mode.
                return Ok(ExecutionResult::success());
            }

            let (key_seq, target) = parse_key_sequence_and_readline_target(key_sequence.as_str())?;
            bind_key_sequence_to_readline_target(&mut *bindings, key_seq, target)?;
        }

        drop(bindings);

        Ok(ExecutionResult::success())
    }
}

fn parse_key_sequence(input: &str) -> Result<interfaces::KeySequence, BindError> {
    // First trim any whitespace.
    let input = input.trim();

    let parsed = brush_parser::readline_binding::parse_key_sequence(input)?;
    let abstract_seq = key_sequence_to_abstract_strokes(&parsed)?;

    Ok(abstract_seq)
}

fn parse_key_sequence_and_shell_command(
    input: &str,
) -> Result<(interfaces::KeySequence, String), BindError> {
    tracing::debug!(target: trace_categories::INPUT,
        "parsing key binding entry: '{input}'"
    );

    // First trim any whitespace.
    let input = input.trim();

    // This should be something of the form:
    //     "KEY-SEQUENCE": SHELL-COMMAND
    let binding = brush_parser::readline_binding::parse_key_sequence_shell_cmd_binding(input)?;
    let abstract_seq = key_sequence_to_abstract_strokes(&binding.seq)?;

    Ok((abstract_seq, binding.shell_cmd))
}

#[derive(Debug)]
#[allow(dead_code, reason = "not all variants implemented yet")]
enum BindableReadlineTarget {
    Function(interfaces::InputFunction),
    Macro(interfaces::KeySequence),
}

fn parse_key_sequence_and_readline_target(
    input: &str,
) -> Result<(interfaces::KeySequence, BindableReadlineTarget), BindError> {
    tracing::debug!(target: trace_categories::INPUT,
        "parsing key binding entry: '{input}'"
    );

    // First trim any whitespace.
    let input = input.trim();

    // This should be of one of these forms:
    //     "KEY-SEQUENCE":function-name
    //     "KEY-SEQUENCE":readline-command
    let binding = brush_parser::readline_binding::parse_key_sequence_readline_binding(input)?;
    let abstract_seq = key_sequence_to_abstract_strokes(&binding.seq)?;

    match binding.target {
        brush_parser::readline_binding::ReadlineTarget::Function(func_name) => {
            let func = parse_readline_function(func_name.as_str())?;
            Ok((abstract_seq, BindableReadlineTarget::Function(func)))
        }
        brush_parser::readline_binding::ReadlineTarget::Macro(target_seq_str) => {
            let parsed_target =
                brush_parser::readline_binding::parse_key_sequence(&target_seq_str)?;
            let abstract_target = key_sequence_to_abstract_strokes(&parsed_target)?;
            Ok((abstract_seq, BindableReadlineTarget::Macro(abstract_target)))
        }
    }
}

fn bind_key_sequence_to_shell_cmd(
    bindings: &mut dyn interfaces::KeyBindings,
    key_sequence: interfaces::KeySequence,
    command: String,
) -> Result<(), BindError> {
    tracing::debug!(target: trace_categories::INPUT,
        "binding key sequence: '{key_sequence}' => command '{command}'"
    );

    bindings.bind(key_sequence, interfaces::KeyAction::ShellCommand(command))?;

    Ok(())
}

fn bind_key_sequence_to_readline_target(
    bindings: &mut dyn interfaces::KeyBindings,
    key_sequence: interfaces::KeySequence,
    target: BindableReadlineTarget,
) -> Result<(), BindError> {
    match target {
        BindableReadlineTarget::Function(func) => {
            tracing::debug!(target: trace_categories::INPUT,
                "binding key sequence: '{key_sequence}' => readline function '{func}'"
            );

            if matches!(func, interfaces::InputFunction::ViEditingMode) {
                // NOTE(vi): We don't support vi mode; silently ignore.
                return Ok(());
            }

            bindings.bind(key_sequence, interfaces::KeyAction::DoInputFunction(func))?;
        }
        BindableReadlineTarget::Macro(cmd_macro) => {
            tracing::debug!(target: trace_categories::INPUT,
                "binding key sequence: '{key_sequence}' => readline macro '{cmd_macro}'"
            );

            bindings.define_macro(key_sequence, cmd_macro)?;
        }
    }

    Ok(())
}

fn key_sequence_to_abstract_strokes(
    seq: &brush_parser::readline_binding::KeySequence,
) -> Result<interfaces::KeySequence, BindError> {
    let phys_strokes = brush_parser::readline_binding::key_sequence_to_strokes(seq)?;

    // Lift from key codes to abstract keys.
    let mut abstract_strokes = vec![];
    let mut key_code_bytes = vec![];
    let mut uninterpretable = false;
    for mut phys_stroke in phys_strokes {
        let mut key = sys::input::try_get_key_from_key_code(phys_stroke.key_code.as_slice());

        // If we couldn't interpret it directly but we see it starts with the escape character,
        // try to see if we can parse it as an Alt+<key> sequence.
        if key.is_none() && phys_stroke.key_code.len() > 1 && phys_stroke.key_code[0] == b'\x1b' {
            key = sys::input::try_get_key_from_key_code(&phys_stroke.key_code[1..]);
            if key.is_some() {
                phys_stroke.meta = true;
            }
        }

        // When storing as bytes, apply control modifier to the key code.
        let mut raw_bytes = phys_stroke.key_code.clone();
        if phys_stroke.control {
            for byte in &mut raw_bytes {
                // Control characters are computed by ANDing with 0x1F
                *byte &= 0x1F;
            }
        }
        key_code_bytes.push(raw_bytes);

        if let Some(key) = key {
            abstract_strokes.push(interfaces::KeyStroke {
                alt: phys_stroke.meta,
                control: phys_stroke.control,
                shift: false,
                key,
            });
        } else {
            uninterpretable = true;
        }
    }

    if uninterpretable {
        Ok(interfaces::KeySequence::Bytes(key_code_bytes))
    } else {
        Ok(interfaces::KeySequence::Strokes(abstract_strokes))
    }
}

fn parse_readline_function(func_name: &str) -> Result<interfaces::InputFunction, BindError> {
    interfaces::InputFunction::from_str(func_name)
        .map_err(|_err| BindError::UnknownKeyBindingFunction(func_name.to_owned()))
}

const fn to_onoff(value: bool) -> &'static str {
    if value { "on" } else { "off" }
}

fn display_funcs_and_bindings(
    bindings: &dyn interfaces::KeyBindings,
    context: &brush_core::ExecutionContext<'_, impl brush_core::ShellExtensions>,
    reusable: bool,
) -> Result<(), BindError> {
    let mut sequences_by_func: HashMap<InputFunction, Vec<KeySequence>> = HashMap::new();
    for (seq, action) in &bindings.get_current() {
        let KeyAction::DoInputFunction(func) = action else {
            continue;
        };

        sequences_by_func
            .entry(func.clone())
            .or_default()
            .push(seq.clone());
    }

    let sorted_funcs = interfaces::InputFunction::iter().sorted_by_key(|f| f.to_string());

    for func in sorted_funcs {
        match sequences_by_func.get(&func) {
            Some(seqs) if reusable => {
                for seq in seqs {
                    writeln!(context.stdout(), "\"{seq}\": {func}")?;
                }
            }
            Some(seqs) => {
                writeln!(
                    context.stdout(),
                    "{func} can be found on {}.",
                    seqs.iter().map(|seq| std::format!("\"{seq}\"")).join(", ")
                )?;
            }
            None if reusable => {
                writeln!(context.stdout(), "# {func} (not bound)")?;
            }
            None => {
                writeln!(context.stdout(), "{func} is not bound to any keys")?;
            }
        }
    }

    Ok(())
}

fn display_macros(
    bindings: &dyn interfaces::KeyBindings,
    context: &brush_core::ExecutionContext<'_, impl brush_core::ShellExtensions>,
    reusable: bool,
) -> Result<(), BindError> {
    for (left, right) in bindings.get_macros() {
        if reusable {
            writeln!(context.stdout(), "\"{left}\": \"{right}\"")?;
        } else {
            writeln!(context.stdout(), "{left} outputs {right}")?;
        }
    }

    Ok(())
}

fn find_key_seqs_bound_to_function(
    bindings: &dyn interfaces::KeyBindings,
    func_str: &str,
) -> Result<Vec<interfaces::KeySequence>, BindError> {
    let Ok(func_to_find) = InputFunction::from_str(func_str) else {
        return Err(BindError::UnknownFunction(func_str.to_owned()));
    };

    let mut found_seqs = vec![];

    for (seq, action) in &bindings.get_current() {
        if let KeyAction::DoInputFunction(func) = action
            && *func == func_to_find
        {
            found_seqs.push(seq.clone());
        }
    }

    Ok(found_seqs)
}

#[cfg(test)]
mod tests {
    use super::*;
    use pretty_assertions::{assert_eq, assert_matches};

    #[test]
    fn parse_example_key_sequence_and_readline_func() {
        let (key_seq, target) =
            parse_key_sequence_and_readline_target(r#""\C-a":beginning-of-line"#).unwrap();

        assert_eq!(
            key_seq,
            interfaces::KeySequence::Strokes(vec![interfaces::KeyStroke {
                alt: false,
                control: true,
                shift: false,
                key: interfaces::Key::Character('a'),
            }])
        );

        assert_matches!(
            target,
            BindableReadlineTarget::Function(interfaces::InputFunction::BeginningOfLine)
        );
    }

    #[test]
    fn parse_escape_char_key_binding() {
        let (key_seq, target) =
            parse_key_sequence_and_readline_target(r#""\er":transpose-chars"#).unwrap();

        assert_eq!(
            key_seq,
            interfaces::KeySequence::Strokes(vec![interfaces::KeyStroke {
                alt: true,
                control: false,
                shift: false,
                key: interfaces::Key::Character('r'),
            }])
        );

        assert_matches!(
            target,
            BindableReadlineTarget::Function(interfaces::InputFunction::TransposeChars)
        );
    }
}