use super::verse::Verse;
use crate::iobtask;
use crate::{btask, ctask, task};
use core::fmt;
use libc::waitpid;
use libc::WNOHANG;
use std::fs::OpenOptions;
use std::io::{self, Read, Write};
use std::os::unix::process::CommandExt;
use std::process::{Command, Stdio};
use std::sync::{Arc, Mutex};

/// Describes one or two characters from the input
///
/// [Rune]s are a way to mark special characters from the input string (i.e.
/// poetry). Some [Rune]s are special--as they denote the end of a [Verse]--
/// and are refered to as a Meter. For instance, `Addendum`, `Couplet`,
/// `Quiet`, and `And`, are all meters. Meters also determine how the
/// [Stanza][super::stanza::Stanza] should be interpreted. For instance, a
/// [Stanza][super::stanza::Stanza] that is piped needs to have
/// its `STDOUT` captured (rather than printing out to the terminal), and
/// subsequently sent to the next [Verse] in the [Poem][super::super::Poem].
///
/// # Values
/// * `None` - A shell command with no additional actions (the end of a poem)
/// * `Pause` - The space character, to dilineate words (` `)
/// * `Path` - The forward slash character, to dilineate paths (`/`)
/// * `Remark` - Indicates a single line comment (`#`)
/// * `String` - Interpret all character as one large
///              [Word][super::word::Word] (`'` or `"`)
/// * `Poem` - A subcommand to run first (`\``)
/// * `Read` - Read files into STDIN (`<`)
/// * `Write` - Write STDOUT to a file (`>`)
/// * `Addendum` - Append STDOUT to a file (`>>`)
/// * `Couplet` - Pipe the output of this command into the next (`|`)
/// * `Quiet` - Fork the called process into the background (`&`)
/// * `And` - Run the next command only if this one succeeds (`&&`)
/// * `Continue` - String commands together on a single line (`;`)
/// * `Home` - Interpret `~` as `$HOME`
/// * `Else` - Any other character
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub enum Rune {
    None,     // No meter (the end of a poem)
    Pause,    // A space
    Path,     // A forward slash
    Remark,   // A comment
    String,   // Interpret the following as one large [Word]
    Poem,     // Run a sub-poem before the main one
    Read,     // Read files into STDIN
    Write,    // Send STDOUT to a file
    Addendum, // Append STDOUT to a file
    Couplet,  // Pipe the output of this command into the next
    Quiet,    // Fork the command into the background
    And,      // Run the next command only if this succeeds
    Continue, // Run the next command, even if this doesn't succeed
    Home,     // Interpret '~' as $HOME
    Else,     // Any other character
}

impl fmt::Display for Rune {
    /// Determine how to print out a [Rune]
    ///
    /// Each [Rune]'s symbol corresponds to its input.
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let rune = match self {
            Rune::None => "",
            Rune::Pause => " ",
            Rune::Path => "/",
            Rune::Remark => "#",
            Rune::String => "\"",
            Rune::Poem => "`",
            Rune::Read => "<",
            Rune::Write => ">",
            Rune::Addendum => ">>",
            Rune::Couplet => "|",
            Rune::Quiet => "&",
            Rune::And => "&&",
            Rune::Continue => ";",
            Rune::Home => "~",
            Rune::Else => "_",
        };

        write!(f, "{}", rune)
    }
}

impl Rune {
    // /// Check if a character is a special [Rune]
    // pub fn special(rune: char) -> bool {
    //     match rune {
    //         ' ' | '/' | '$' | '\'' | '"' | '`' | '<' | '>' | '|' | '&' | ';' | '~' => true,
    //         _ => false,
    //     }
    // }

    /// Recite a verse with [Rune::None]
    ///
    /// Call this function on a [Verse] with a meter of type [Rune::None].
    /// This forks into a child process, calls the `verb()` (i.e. program)
    /// that was specified in the [Verse], then waits for that program to
    /// complete. If the last [Verse] piped its contents into `out`, it will
    /// be piped into the STDIN of this [Verse]. If all Rust code is called
    /// successfully, return the exit code of the process. Otherwise, return a
    /// [std::io::Error].
    ///
    /// # Arguments
    /// * `verse: &Verse` - The verse to recite
    /// * `out: &mut String` - A string that may have output from the last command
    pub fn incant_none(verse: &Verse, out: &mut String) -> Result<i32, io::Error> {
        let child = task!(verse, out);

        let output = child.wait_with_output()?;

        if !output.status.success() {
            return Ok(output.status.code().unwrap_or(-1));
        }

        Ok(output.status.code().unwrap_or(0))
    }

    /// Recite a verse with [Rune::Couplet]
    ///
    /// Call this function on a [Verse] with a meter of type [Rune::Couplet].
    /// This forks into a child process, calls the `verb` (i.e. program)
    /// that was specified in the [Verse], then waits for that program to
    /// complete. If the last [Verse] piped its contents into `out`, it will
    /// be piped into the STDIN of this [Verse]. Then, the contents of this
    /// processes' STDOUT are stored in `out`. If all Rust code is called
    /// successfully, return the exit code of the process. Otherwise, return a
    /// [std::io::Error].
    ///
    /// # Arguments
    /// * `verse: &Verse` - The verse to recite
    /// * `out: &mut String` - A string that may have output from the last command
    pub fn incant_couplet(verse: &Verse, out: &mut String) -> Result<i32, io::Error> {
        let child = ctask!(verse, out);

        let output = child.wait_with_output()?;

        if !output.status.success() {
            return Ok(output.status.code().unwrap_or(-1));
        }

        out.push_str(
            String::from_utf8_lossy(&output.stdout)
                .into_owned()
                .as_str(),
        );

        Ok(output.status.code().unwrap_or(0))
    }

    /// Recite a verse with [Rune::Quiet]
    ///
    /// Call this function on a [Verse] with a meter of type [Rune::Quiet].
    /// This forks a child process into the background. It then registers a
    /// `SIGCHLD` handler, making sure to do so for each PID in the `pids`
    /// Vec. If the last [Verse] piped its contents into `out`, it will be
    /// piped into the STDIN of this [Verse]. If all Rust code is called
    /// successfully, return the exit code of the process. Otherwise, return a
    /// [std::io::Error].
    ///
    /// # Arguments
    /// * `verse: &Verse` - The verse to recite
    /// * `out: &mut String` - A string that may have output from the last command
    /// * `pids: Arc<Mutex<Vec<i32>>>` - A vector that stores the PIDs of all background processes that belong to the shell
    pub fn incant_quiet(
        verse: &Verse,
        out: &mut String,
        pids: &mut Arc<Mutex<Vec<i32>>>,
    ) -> Result<i32, io::Error> {
        let child = btask!(verse, out);
        println!("[&]  {}", child.id());

        pids.lock().unwrap().push(child.id() as i32);
        let stanza = verse.stanza.join(" ").to_string();
        let pids = Arc::clone(pids);

        unsafe {
            signal_hook::low_level::register(signal_hook::consts::SIGCHLD, move || {
                for pid in pids.lock().unwrap().iter() {
                    let mut pid = *pid;
                    let mut status: i32 = 0;
                    pid = waitpid(pid, &mut status, WNOHANG);
                    if pid > 0 {
                        print!("\n[&]  + done    {}", stanza);
                        io::stdout().flush().unwrap();
                    }
                }
            })
            .unwrap();
        }

        Ok(0)
    }

    /// Alias to [Rune::incant_none]
    pub fn incant_and(verse: &Verse, out: &mut String) -> Result<i32, io::Error> {
        Rune::incant_none(verse, out)
    }

    /// Alias to [Rune::incant_none]
    pub fn incant_continue(verse: &Verse, out: &mut String) -> Result<i32, io::Error> {
        Rune::incant_none(verse, out)
    }

    /// Recite a verse with [Rune::Read]
    ///
    /// Call this function on a [Verse] with a meter of type [Rune::Read].
    /// This reads the specified files into `out`, then makes a call to
    /// [Rune::incant_none] with all the contents of `out`. Anything piped to
    /// this command will appear in `out` first, and any subsequent files will
    /// be appended.
    ///
    /// # Arguments
    /// * `verse: &Verse` - The verse to recite
    /// * `paths: &Verse` - The next verse (i.e. the file paths)
    /// * `out: &mut String` - A string that may have output from the last command,
    ///                        and that will be used to store the contents of the
    ///                        file paths in `next`
    pub fn incant_read(
        verse: &mut Verse,
        out: &mut String,
        pids: &mut Arc<Mutex<Vec<i32>>>,
    ) -> Result<i32, io::Error> {
        // Split the verse from the paths
        let paths = verse.split("<");

        // Read all file specified in the next verse into 'out', since there
        // may also be piped output from the last command
        for path in paths.iter() {
            let mut file = OpenOptions::new().read(true).open(path)?;
            let mut contents = String::new();
            file.read_to_string(&mut contents)?;
            out.push_str(contents.as_str());
        }

        // Alias incant_<meter>
        match verse.meter {
            Rune::None => Rune::incant_none(&verse, out),
            Rune::Couplet => Rune::incant_couplet(&verse, out),
            Rune::Quiet => Rune::incant_quiet(&verse, out, pids),
            Rune::And => Rune::incant_and(&verse, out),
            Rune::Continue => Rune::incant_continue(&verse, out),
            _ => unreachable!(),
        }
    }

    /// Recite a verse with [Rune::Write]
    ///
    /// Call this function on a [Verse] with a meter of type [Rune::Write].
    /// This writes the output of the verse into the specified files, after
    /// making a call to [Rune::incant_couplet].
    ///
    /// # Arguments
    /// * `verse: &Verse` - The verse to recite
    /// * `paths: &Verse` - The next verse (i.e. the file paths)
    /// * `out: &mut String` - A string that may have output from the last command,
    ///                        and that will be used to store the contents of the
    ///                        file paths in `next`
    pub fn incant_write(
        verse: &mut Verse,
        out: &mut String,
        pids: &mut Arc<Mutex<Vec<i32>>>,
    ) -> Result<i32, io::Error> {
        // Split the verse from the paths
        let paths = verse.split("<");

        // Alias incant_<meter>
        // let status = Rune::incant_couplet(&verse, out)?;
        let status = match verse.meter {
            Rune::None => Rune::incant_none(&verse, out)?,
            Rune::Couplet => Rune::incant_couplet(&verse, out)?,
            Rune::Quiet => Rune::incant_quiet_io(&verse, out, pids)?,
            Rune::And => Rune::incant_and(&verse, out)?,
            Rune::Continue => Rune::incant_continue(&verse, out)?,
            _ => unreachable!(),
        };

        // Write output to each file specified in the next verse
        for path in paths.iter() {
            let mut file = OpenOptions::new().create(true).write(true).open(path)?;
            file.write(out.as_bytes())?;
        }

        // Clear out
        out.clear();

        // Return the exit status
        Ok(status)
    }

    /// Recite a verse with [Rune::Addendum]
    ///
    /// Same as [Rune::Write], except it appends to the file(s) specified,
    /// instead of overwriting them.
    ///
    /// # Arguments
    /// * `verse: &Verse` - The verse to recite
    /// * `paths: &Verse` - The next verse (i.e. the file paths)
    /// * `out: &mut String` - A string that may have output from the last command,
    ///                        and that will be used to store the contents of the
    ///                        file paths in `next`
    pub fn incant_addendum(
        verse: &mut Verse,
        out: &mut String,
        pids: &mut Arc<Mutex<Vec<i32>>>,
    ) -> Result<i32, io::Error> {
        // Split the verse from the paths
        let paths = verse.split("<");

        // Alias incant_<meter>
        // let status = Rune::incant_couplet(&verse, out)?;
        let status = match verse.meter {
            Rune::None => Rune::incant_none(&verse, out)?,
            Rune::Couplet => Rune::incant_couplet(&verse, out)?,
            Rune::Quiet => Rune::incant_quiet_io(&verse, out, pids)?,
            Rune::And => Rune::incant_and(&verse, out)?,
            Rune::Continue => Rune::incant_continue(&verse, out)?,
            _ => unreachable!(),
        };

        // Write output to each file specified in the next verse
        for path in paths.iter() {
            let mut file = OpenOptions::new().create(true).append(true).open(path)?;
            file.write(out.as_bytes())?;
        }

        // Clear out
        out.clear();

        // Return the exit status
        Ok(status)
    }

    /// Same as incant_quiet, except capture STDOUT into `out`
    pub fn incant_quiet_io(
        verse: &Verse,
        out: &mut String,
        pids: &mut Arc<Mutex<Vec<i32>>>,
    ) -> Result<i32, io::Error> {
        let child = iobtask!(verse, out);
        println!("[&]  {}", child.id());

        pids.lock().unwrap().push(child.id() as i32);
        let stanza = verse.stanza.join(" ").to_string();
        let pids = Arc::clone(pids);

        unsafe {
            signal_hook::low_level::register(signal_hook::consts::SIGCHLD, move || {
                for pid in pids.lock().unwrap().iter() {
                    let mut pid = *pid;
                    let mut status: i32 = 0;
                    pid = waitpid(pid, &mut status, WNOHANG);
                    if pid > 0 {
                        print!("\n[&]  + done    {}", stanza);
                        io::stdout().flush().unwrap();
                    }
                }
            })
            .unwrap();
        }

        Ok(0)
    }
}