use super::rune::Rune;
use super::stanza::Stanza;
use super::word::Word;
use crate::poem::anthology;
use crate::poem::anthology::Anthology;
use crate::poem::Poem;
mod logic;
use crate::compose::Environment;
use crate::incant;
use libc::{waitpid, WNOHANG};
use std::fmt::Debug;
use std::fs::OpenOptions;
use std::io::{self, Read, Write};
use std::os::unix::process::CommandExt;
use std::path::Path;
use std::process::{Child, Command, Output, Stdio};
use std::sync::{Arc, Mutex};

/// A [Stanza] and its [meter](Rune)
///
/// In addition to a [Stanza] and a [meter](Rune), this also holds a
/// [bool] value called `couplet`, indicating that it needs to accept
/// input on `STDIN` from the previous [Verse].
#[derive(Debug, Clone)]
pub struct Verse {
    /// A command and its arguments (also see [Stanza])
    pub stanza: Stanza,

    /// Denote the couplet status (for piping text in/out)
    ///
    /// * `0`: Not a couplet
    /// * `1`: Left side of a couplet
    /// * `2`: Right side of a couplet
    /// * `3`: Both sides of a couplet
    ///
    /// ```
    /// ls | grep Ca | lolcat
    /// ^    ^         ^
    /// |    |         2: right side of a couplet
    /// |    3: both sides of a couplet
    /// 1: left side of a couplet
    /// ```
    pub couplet: u8,

    /// A list of IO operations to be performed
    ///
    /// For instance, read into STDIN, write STDOUT to a file, etc. May
    /// be empty. Also see [Rune] for more details.
    pub io: Vec<Rune>,

    /// Input paths
    ///
    /// A list of files to read into STDIN, may be empty.
    pub ip: Stanza,

    /// Output paths
    ///
    /// A list of files to send STDOUT to, may be empty.
    pub op: Stanza,

    /// Error paths
    ///
    /// A list of files to send STDERR to, may be empty.
    pub ep: Stanza,

    /// Internal poems (i.e. 'ls \`ls\`')
    ///
    /// A list of poems to evaluate before evaluating this one.
    pub poems: Vec<Poem>,

    /// Interpret how to handle a poem after forking to its command
    ///
    /// * `None`: Indicates the end of a poem
    /// * `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`: Run the next command, regardless of whether or not
    ///               this command succeeds (`;` or a newline in a file)
    ///
    /// Also see [Rune] for more details.
    pub meter: Rune,
}

/// Granularity for [spellcheck()][Verse::spellcheck]
///
/// Indicates if a given [verb][Verse::verb] exists, and where.
#[derive(Debug, Clone)]
pub enum Spelling {
    /// The [verb][Verse::verb] is a full path, and that path exists
    FullPath,

    /// The [verb][Verse::verb] is on the `$PATH`
    OnPath(usize),

    /// The [verb][Verse::verb] is a built-in shell command
    BuiltIn(usize),
}

pub trait Forkable<T> {
    fn fork(&mut self, env: &mut Environment) -> Result<T, io::Error>;
}

impl Forkable<Child> for Command {
    fn fork(&mut self, _env: &mut Environment) -> Result<Child, io::Error> {
        self.spawn()
    }
}

impl Forkable<Anthology> for Anthology {
    fn fork(&mut self, env: &mut Environment) -> Result<Anthology, io::Error> {
        self.spawn(env)
    }
}

impl Verse {
    /// Create a new [Verse]
    ///
    /// Returns a new [Verse], with an empty [Stanza], a meter of
    /// [Rune::None], and `couplet` set to 0.
    pub fn new() -> Self {
        Verse {
            stanza: Stanza::new(),
            couplet: 0,
            io: Vec::new(),
            ip: Stanza::new(),
            op: Stanza::new(),
            ep: Stanza::new(),
            poems: Vec::new(),
            meter: Rune::None,
        }
    }

    /// Get the [Verse]'s verb
    ///
    /// Return the program to be forked
    pub fn verb(&self) -> String {
        self.stanza[0].clone()
    }

    /// Get the [Verse]'s clause
    ///
    /// Return program arguments, if they exist
    pub fn clause(&self) -> Option<Vec<String>> {
        match self.stanza.len() {
            0 => None,
            1 => None,
            _ => Some(self.stanza[1..].to_vec()),
        }
    }

    /// Alias to [Verse].stanza.push()
    pub fn push(&mut self, word: String) {
        self.stanza.push(word);
    }

    /// Alias to [Verse].stanza.is_empty()
    pub fn is_empty(&self) -> bool {
        self.stanza.is_empty()
    }

    /// Alias to [Verse].stanza.clear()
    pub fn clear(&mut self) {
        self.stanza.clear();
        self.io.clear();
        self.poems.clear();
    }

    /// Check if the [Verse] contains any internal poems
    pub fn poems(&self) -> bool {
        if self.poems.len() > 0 {
            return true;
        }
        false
    }

    /// Push a word to the [Verse]'s [Stanza]
    ///
    /// Push a word to the [Verse]'s [Stanza], or one of its IO
    /// channels. If `word` is empty, this function will simply return
    /// without performing any operations. A channel of [None] will push
    /// to the [Verse]'s [Stanza], while IO [Rune]s will determine which
    /// IO channel a word will get pushed onto.
    ///
    /// # Arguments
    /// word - The word to push onto the [Stanza]/channel
    /// channel - Specifiy which channel to use
    ///
    /// # Examples
    /// ```
    /// word.push("c");
    /// word.push("a");
    /// word.push("t");
    /// verse.add(&mut word, None); // Pushes onto [Stanza]
    /// verse.add(&mut word, Some(Rune::Write)); // Pushes onto [op]
    /// verse.add(&mut word, Some(Rune::WriteAll)); // Pushes onto [op], [ep]
    /// ```
    pub fn add(&mut self, word: &mut Word, channel: Option<Rune>) {
        // Do nothing if the stack is empty
        if word.is_empty() {
            return;
        }

        // Push the word
        match channel {
            Some(Rune::Read) => self.ip.push(word.iter().collect()),
            Some(Rune::Write) | Some(Rune::Addendum) => self.op.push(word.iter().collect()),
            Some(Rune::Write2) | Some(Rune::Addendum2) => self.ep.push(word.iter().collect()),
            Some(Rune::WriteAll) | Some(Rune::AddendumAll) => {
                self.op.push(word.iter().collect());
                self.ep.push(word.iter().collect());
            }
            Some(_) | None => self.push(word.iter().collect()),
        }

        // Clear the stack
        word.clear();
    }

    /// Check if the [verb][Verse::verb] exists
    ///
    /// First checks if the [verb][Verse::verb] is a built-in shell
    /// command. Then checks if the [verb][Verse::verb] is on the
    /// `$PATH`. If not, then the [verb][Verse::verb] is a either a full
    /// path, or it does not exist on the system.
    ///
    /// # Examples
    /// ```
    /// let command_full_path = vec!["/bin/ls"]
    ///                         .into_iter()
    ///                         .map(String::from)
    ///                         .collect<Vec<String>>();
    ///
    /// let command_on_path = vec!["cargo", "build", "--release"]
    ///                       .into_iter()
    ///                       .map(String::from)
    ///                       .collect<Vec<String>>();
    ///
    /// let command_built_in = vec!["alias", "g=git"]
    ///                        .into_iter()
    ///                        .map(String::from)
    ///                        .collect<Vec<String>>();
    ///
    /// let command_no_exist = vec!["thisdoesntexist"]
    ///                        .into_iter()
    ///                        .map(String::from)
    ///                        .collect<Vec<String>>();
    ///
    /// let verse = Verse::new();
    /// verse.stanza = Stanza::new(command_full_path);
    /// verse.spellcheck(&env.bins); // -> Some(Spelling::FullPath)
    ///
    /// let verse = Verse::new();
    /// verse.stanza = Stanza::new(command_on_path);
    /// verse.spellcheck(&env.bins); // -> Some(Spelling::OnPath)
    ///
    /// let verse = Verse::new();
    /// verse.stanza = Stanza::new(command_built_in);
    /// verse.spellcheck(&env.bins); // -> Some(Spelling::BuiltIn)
    ///
    /// let verse = Verse::new();
    /// verse.stanza = Stanza::new(command_no_exist);
    /// verse.spellcheck(&env.bins); // -> None
    /// ```
    pub fn spellcheck(&self, bins: &Vec<String>) -> Option<Spelling> {
        // An empty verb (i.e. the empty string) cannot be a program, so
        // return false
        // Thanks to the parsing in Poem::read, however, it's
        // unlikely for this to happen
        if self.verb().is_empty() {
            return None;
        }

        // Check for built-ins
        let i = anthology::lookup(self.verb().as_str());
        match i {
            Some(i) => return Some(Spelling::BuiltIn(i)),
            None => {}
        };

        // Only search the $PATH if a full or relative path was not given, or
        // if the path given does not exist
        if !Path::new(self.verb().as_str()).exists() {
            // Try to find a binary in our path with the same name as the verb
            // Searches in $PATH order
            for (i, path) in bins.iter().enumerate() {
                if path.split('/').last().unwrap() == self.verb() {
                    return Some(Spelling::OnPath(i));
                }
            }

            // If it was not found, return None
            return None;
        }

        // Return the length of bins if the full path or relative path exists
        Some(Spelling::FullPath)
    }

    /// Run a command
    ///
    /// The [recite()][crate::poem::recite] function calls this
    /// [incant()][Verse::incant] function for each verse it contains.
    /// This function handles the actual setup and spawning (forking) of
    /// a new process specified in the [Verse]. It will also run IO
    /// operations for the verse, and setup appropriate coupling, as per
    /// the [Verse]'s own details, contained throughout its fields.
    pub fn incant(
        &mut self,
        out: &mut Vec<u8>,
        pids: &mut Arc<Mutex<Vec<i32>>>,
        env: &mut Environment,
        spell: Option<Spelling>,
    ) -> Result<i32, io::Error> {
        // Read files into 'out' if Rune::Read is present in the verse's IO
        if self.io.contains(&Rune::Read) {
            // Enable piping on stdin
            self.couplet += 2;

            // Read all files specified after '<' into 'out', since there may
            // also be piped output from the last command
            for path in self.ip.iter() {
                let mut file = OpenOptions::new().read(true).open(path)?;
                let mut contents = String::new();
                file.read_to_string(&mut contents)?;
                out.append(&mut contents.as_bytes().to_vec());
            }
        }

        // Build and run the command
        match spell {
            Some(Spelling::BuiltIn(i)) => {
                let mut command = Anthology::new(i);
                incant!(self.verb(), command, out, pids, env, self)
            }
            _ => {
                let mut command = Command::new(self.verb());
                incant!(self.verb(), command, out, pids, env, self)
            }
        }
    }
}