use crate::{
    resolve_path, Error, Instruction, Instructions, Result, ScriptParser,
};
use anticipate::{
    log::{LogWriter, NoopLogWriter, PrefixLogWriter, StandardLogWriter},
    repl::ReplSession,
    spawn_with_options, ControlCode, Expect, Regex, Session,
};
use ouroboros::self_referencing;
use probability::prelude::*;
use std::io::{BufRead, Write};
use std::{
    borrow::Cow,
    path::{Path, PathBuf},
    process::Command,
    thread::sleep,
    time::Duration,
};
use tracing::{span, Level};
use unicode_segmentation::UnicodeSegmentation;

const PROMPT: &str = "➜ ";

#[cfg(unix)]
const COMMAND: &str = "bash -noprofile -norc";
#[cfg(windows)]
const COMMAND: &str = "pwsh -NoProfile -NonInteractive -NoLogo";

/// Source for probability distribution.
struct Source<T>(T);

impl<T: rand::RngCore> source::Source for Source<T> {
    fn read_u64(&mut self) -> u64 {
        self.0.next_u64()
    }
}

/// Options for asciinema execution.
#[derive(Debug, Clone)]
pub struct CinemaOptions {
    /// Delay in milliseconds.
    pub delay: u64,
    /// Type pragma command.
    pub type_pragma: bool,
    /// Deviation for gaussian delay modification.
    pub deviation: f64,
    /// Shell to run.
    pub shell: String,
    /// Terminal columns.
    pub cols: u64,
    /// Terminal rows.
    pub rows: u64,
}

impl Default for CinemaOptions {
    fn default() -> Self {
        Self {
            delay: 75,
            type_pragma: false,
            deviation: 15.0,
            shell: COMMAND.to_string(),
            cols: 80,
            rows: 24,
        }
    }
}

/// Options for the interpreter.
pub struct InterpreterOptions {
    /// Command to execute in the pty.
    pub command: String,
    /// Timeout for rexpect.
    pub timeout: Option<u64>,
    /// Options for asciinema.
    pub cinema: Option<CinemaOptions>,
    /// Identifier.
    pub id: Option<String>,
    /// Prompt.
    pub prompt: Option<String>,
    /// Echo to stdout.
    pub echo: bool,
    /// Format IO logged to stdout.
    pub format: bool,
    /// Print comments.
    pub print_comments: bool,
}

impl Default for InterpreterOptions {
    fn default() -> Self {
        Self {
            command: COMMAND.to_owned(),
            prompt: None,
            timeout: Some(10000),
            cinema: None,
            id: None,
            echo: false,
            format: false,
            print_comments: false,
        }
    }
}

impl InterpreterOptions {
    /// Create interpreter options.
    pub fn new(
        timeout: u64,
        echo: bool,
        format: bool,
        print_comments: bool,
    ) -> Self {
        Self {
            command: COMMAND.to_owned(),
            prompt: None,
            timeout: Some(timeout),
            cinema: None,
            id: None,
            echo,
            format,
            print_comments,
        }
    }

    /// Create interpreter options for asciinema recording.
    pub fn new_recording(
        output: impl AsRef<Path>,
        overwrite: bool,
        options: CinemaOptions,
        timeout: u64,
        echo: bool,
        format: bool,
        print_comments: bool,
    ) -> Self {
        let mut command = format!(
            "asciinema rec {:#?}",
            output.as_ref().to_string_lossy(),
        );
        if overwrite {
            command.push_str(" --overwrite");
        }
        command.push_str(&format!(" --rows={}", options.rows));
        command.push_str(&format!(" --cols={}", options.cols));
        Self {
            command,
            prompt: None,
            timeout: Some(timeout),
            cinema: Some(options),
            id: None,
            echo,
            format,
            print_comments,
        }
    }
}

/// Script file.
#[derive(Debug)]
pub struct ScriptFile {
    path: PathBuf,
    source: ScriptSource,
}

impl ScriptFile {
    /// Path to the source file.
    pub fn path(&self) -> &PathBuf {
        &self.path
    }

    /// Source contents of the file.
    pub fn source(&self) -> &str {
        self.source.borrow_source()
    }

    /// Script instructions.
    pub fn instructions(&self) -> &Instructions<'_> {
        self.source.borrow_instructions()
    }
}

#[self_referencing]
#[derive(Debug)]
/// Script file.
pub struct ScriptSource {
    /// Script source.
    pub source: String,
    /// Parsed instructions.
    #[borrows(source)]
    #[covariant]
    pub instructions: Instructions<'this>,
}

impl ScriptFile {
    /// Parse a collection of files.
    pub fn parse_files(paths: Vec<PathBuf>) -> Result<Vec<ScriptFile>> {
        let mut results = Vec::new();
        for path in paths {
            let script = Self::parse(path)?;
            results.push(script);
        }
        Ok(results)
    }

    /// Parse a single file.
    pub fn parse(path: impl AsRef<Path>) -> Result<ScriptFile> {
        let source = Self::parse_source(path.as_ref())?;
        Ok(ScriptFile {
            path: path.as_ref().to_owned(),
            source,
        })
    }

    fn parse_source(path: impl AsRef<Path>) -> Result<ScriptSource> {
        let mut includes = Vec::new();
        let source = std::fs::read_to_string(path.as_ref())?;
        let mut source = ScriptSourceTryBuilder {
            source,
            instructions_builder: |source| {
                let (instructions, mut file_includes) =
                    ScriptParser::parse_file(source, path.as_ref())?;
                includes.append(&mut file_includes);
                Ok::<_, Error>(instructions)
            },
        }
        .try_build()?;

        let mut num_inserts = 0;
        for raw in includes {
            let src = Self::parse_source(&raw.path)?;
            let instruction = Instruction::Include(src);
            source.with_instructions_mut(|i| {
                let index = raw.index + num_inserts;
                if index < i.len() {
                    i.insert(index, instruction);
                } else {
                    i.push(instruction);
                }
                num_inserts += 1;
            });
        }

        Ok(source)
    }

    /// Execute the command and instructions in a pseudo-terminal.
    pub fn run(&self, options: InterpreterOptions) -> Result<()> {
        let cmd = options.command.clone();

        let span = if let Some(id) = &options.id {
            span!(Level::DEBUG, "run", id = id)
        } else {
            span!(Level::DEBUG, "run")
        };

        let _enter = span.enter();

        let instructions = self.source.borrow_instructions();
        let is_cinema = options.cinema.is_some();

        let prompt =
            options.prompt.clone().unwrap_or_else(|| PROMPT.to_owned());
        std::env::set_var("PS1", &prompt);

        if let Some(cinema) = &options.cinema {
            // Export a vanilla shell for asciinema
            let shell = format!("PS1='{}' {}", &prompt, cinema.shell);
            std::env::set_var("SHELL", shell);
        }

        let pragma =
            if let Some(Instruction::Pragma(cmd)) = instructions.first() {
                Some(resolve_path(&self.path, cmd)?)
            } else {
                None
            };

        let exec_cmd = if let (false, Some(pragma)) = (is_cinema, &pragma) {
            pragma.as_ref().to_owned()
        } else {
            cmd.to_owned()
        };

        tracing::info!(exec = %exec_cmd, "run");

        let timeout = options
            .timeout
            .as_ref()
            .map(|val| Duration::from_millis(*val));

        let cmd = parse_command(&exec_cmd)?;
        if !options.echo && !options.format {
            let pty: Session<NoopLogWriter> =
                spawn_with_options(cmd, None, timeout)?;
            start(pty, prompt, options, pragma, instructions)?;
        } else if options.echo && !options.format {
            let pty = spawn_with_options(
                cmd,
                Some(StandardLogWriter::default()),
                timeout,
            )?;
            start(pty, prompt, options, pragma, instructions)?;
        } else if options.echo && options.format {
            let pty = spawn_with_options(
                cmd,
                Some(PrefixLogWriter::default()),
                timeout,
            )?;
            start(pty, prompt, options, pragma, instructions)?;
        }

        Ok(())
    }
}

fn parse_command(cmd: &str) -> Result<Command> {
    let mut parts = comma::parse_command(cmd)
        .ok_or(Error::BadArguments(cmd.to_owned()))?;
    let prog = parts.remove(0);
    let mut command = Command::new(prog);
    command.args(parts);
    Ok(command)
}

fn start<O: LogWriter>(
    session: Session<O>,
    prompt: String,
    options: InterpreterOptions,
    pragma: Option<Cow<'_, str>>,
    instructions: &[Instruction<'_>],
) -> Result<()> {
    let mut p = ReplSession::new(session, prompt, None, false);

    if options.cinema.is_some() {
        p.expect_prompt()?;
        // Wait for the initial shell prompt to flush
        sleep(Duration::from_millis(50));
        tracing::debug!("ready");
    }

    exec(
        &mut p,
        instructions,
        &options,
        pragma.as_ref().map(|i| i.as_ref()),
    )?;

    if options.cinema.is_some() {
        tracing::debug!("exit");
        p.send(ControlCode::EndOfTransmission)?;
    } else {
        tracing::debug!("eof");
        // If it's not a shell, ie: has a pragma command
        // which is a script this will fail with I/O error
        // but we can safely ignore it
        let _ = p.send(ControlCode::EndOfTransmission);
    }

    Ok(())
}

fn type_text<O: LogWriter>(
    pty: &mut ReplSession<O>,
    text: &str,
    cinema: &CinemaOptions,
) -> Result<()> {
    for c in UnicodeSegmentation::graphemes(text, true) {
        pty.send(c)?;
        pty.flush()?;

        let mut source = Source(rand::rngs::OsRng);
        let gaussian = Gaussian::new(0.0, cinema.deviation);
        let drift = gaussian.sample(&mut source);

        let delay = if (drift as u64) < cinema.delay {
            let drift = drift as i64;
            if drift < 0 {
                cinema.delay - drift.unsigned_abs()
            } else {
                cinema.delay + drift as u64
            }
        } else {
            cinema.delay + drift.abs() as u64
        };

        sleep(Duration::from_millis(delay));
    }

    pty.send("\n")?;
    pty.flush()?;

    Ok(())
}

fn exec<O: LogWriter>(
    p: &mut ReplSession<O>,
    instructions: &[Instruction<'_>],
    options: &InterpreterOptions,
    pragma: Option<&str>,
) -> Result<()> {
    for cmd in instructions.iter() {
        tracing::debug!(instruction = ?cmd);
        match cmd {
            Instruction::Pragma(_) => {
                if let (Some(cinema), Some(cmd)) = (&options.cinema, &pragma)
                {
                    if cinema.type_pragma {
                        type_text(p, cmd, cinema)?;
                    } else {
                        p.send_line(cmd)?;
                    }
                }
            }
            Instruction::Sleep(delay) => {
                sleep(Duration::from_millis(*delay));
            }
            Instruction::Send(line) => {
                p.send(line)?;
            }
            Instruction::Comment(line) | Instruction::SendLine(line) => {
                if let (false, Instruction::Comment(_)) =
                    (options.print_comments, cmd)
                {
                    continue;
                }

                let line = ScriptParser::interpolate(line)?;
                if let Some(cinema) = &options.cinema {
                    type_text(p, line.as_ref(), cinema)?;
                } else {
                    p.send_line(line.as_ref())?;
                }
            }
            Instruction::SendControl(ctrl) => {
                let ctrl = ControlCode::try_from(*ctrl).map_err(|_| {
                    Error::InvalidControlCode(ctrl.to_string())
                })?;
                p.send(ctrl)?;
            }
            Instruction::Expect(line) => {
                p.expect(line)?;
            }
            Instruction::Regex(line) => {
                p.expect(Regex(line))?;
            }
            Instruction::ReadLine => {
                let mut line = String::new();
                p.read_line(&mut line)?;
            }
            Instruction::Wait => {
                p.expect_prompt()?;
            }
            Instruction::Clear => {
                p.send_line("clear")?;
            }
            Instruction::Flush => {
                p.flush()?;
            }
            Instruction::Include(source) => {
                exec(p, source.borrow_instructions(), options, pragma)?;
            }
        }

        sleep(Duration::from_millis(15));
    }
    Ok(())
}