use super::{
    elements::{rune::Rune, verse::Verse, word::Word},
    Poem,
};
use core::fmt;
mod parse;
use crate::compose::Environment;
use crate::{poem, remark, string};
use parse::next;

/// Custom errors for the parser ([read()][crate::poem::read])
#[derive(Debug, PartialEq, Eq)]
pub enum Mishap {
    /// Generic parser error
    ParseMishap(usize, usize, char),

    /// IO operation parse errors
    ///
    /// Raised when an IO operation is specified, but a filepath was not
    /// given.
    ///
    /// # Examples
    /// ```sh
    /// cat < # No file specified for Rune::Read
    /// cat file.txt >> # No file specified for Rune::Addendum
    /// ```
    IOMishap(usize, usize, char),

    /// Missing end character
    ///
    /// Some [Rune]s consists of two characters, that may contain other
    /// characters between them (i.e. [String][Rune::String]). This is
    /// raised when the ending character was left out.
    ///
    /// # Examples
    /// ```sh
    /// echo 'Hello # Ending ' character is missing
    /// mv file.txt hello.txt" # Beginning " character is missing
    /// ```
    PartialMishap(usize, usize, char),
}

impl fmt::Display for Mishap {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let message = match self {
            Mishap::ParseMishap(j, i, c) => {
                format!("parse error on line {} pos {} near '{}'", j, i, c)
            }
            Mishap::IOMishap(j, i, c) => {
                format!(
                    "must provide file for io operation on line {} pos {} near '{}'",
                    j, i, c
                )
            }
            Mishap::PartialMishap(j, i, c) => {
                format!(
                    "partial string or action on line {} pos {} near '{}'",
                    j, i, c
                )
            }
        };

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

/// A [Poem] can add more [Verse]s to itself
trait Appendable {
    type Type;
    fn add(
        &mut self,
        verse: &mut Self::Type,
        meter: Rune,
        env: &mut Environment,
    ) -> Result<(), Mishap>;
}

impl Appendable for Poem {
    type Type = Verse;

    /// Push a [Verse] to the [Poem]
    ///
    /// Push a [Verse] to the [Poem] after checking that the [Verse] is
    /// not empty. It also:
    ///  - sets the meter of the [Verse],
    ///  - determines the couplet status of the [Verse],
    ///  - and checks for aliases associated the the [Verse]'s verb.
    ///
    /// Once the [Verse] is pushed to the [Poem], the verse stack is
    /// cleared.
    ///
    /// # Examples
    /// ```
    /// ...
    /// verse.push("cat");
    /// verse.push("Cargo.toml");
    /// poem.add(&mut verse, Rune::None, &mut env);
    /// ```
    fn add(
        &mut self,
        verse: &mut Self::Type,
        meter: Rune,
        env: &mut Environment,
    ) -> Result<(), Mishap> {
        if verse.is_empty() {
            return Ok(());
        }

        // Get meter of the last verse
        let last = match self.last() {
            Some(last) => last.meter,
            None => Rune::Else,
        };

        // Check the meter
        verse.meter = meter;
        if last == Rune::Couplet && meter == Rune::Couplet {
            verse.couplet = 3;
        } else if last == Rune::Couplet {
            verse.couplet = 2;
        } else if meter == Rune::Couplet {
            verse.couplet = 1;
        }

        // Check for aliases
        match env.aliases.get(&verse.verb()) {
            Some(alias) if env.cs == 0 => {
                // Increase the callstack
                env.cs = 1;

                // Interpret the alias (could be a complex poem)
                let mut poem = Poem::read(alias.to_string(), env)?;

                // Decrease the callstack
                env.cs = 0;

                // Try and get the last verse
                let lv = match poem.last_mut() {
                    Some(lv) => lv,
                    None => unreachable!(), // Should be caught by a Mishap above
                };

                // The last verse inherits the traits from the original
                if verse.couplet > 0 {
                    lv.couplet = verse.couplet;
                }
                lv.io = verse.io.clone();
                lv.op = verse.op.clone();
                lv.ep = verse.ep.clone();
                lv.poems = verse.poems.clone();
                lv.meter = verse.meter;
                if verse.clause().is_some() {
                    for word in verse.clause().unwrap().iter() {
                        lv.stanza.push(word.to_string());
                    }
                }

                // Push verse(s)
                for v in poem.iter() {
                    self.push(v.clone());
                }
            }
            Some(_) | None => {
                // Push verse(s)
                self.push(verse.clone());
            }
        }

        // Clear the current verse stack
        verse.clear();

        // Unit
        Ok(())
    }
}

/// A [Poem] can parse poetry
pub trait Readable {
    fn read(poetry: String, env: &mut Environment) -> Result<Poem, Mishap>;
}

impl Readable for Poem {
    /// Parse a [Poem] from a raw [String] input
    ///
    /// Takes a shell command/program or file and converts it to a
    /// machine-runnable [Poem]. If there is a parse error,
    /// [read()][Poem::read] may return a [Mishap]. See
    /// [recite()][crate::poem::recite] or [incant()][Verse::incant] for
    /// how each [Verse] in a [Poem] is called.
    fn read(poetry: String, env: &mut Environment) -> Result<Poem, Mishap> {
        // Get all the characters in the input string as an iterator
        let mut chars = poetry.chars().into_iter();

        // Create a stack to store words
        let mut word: Word = Word::new();

        // Create a stack to store the current verse
        let mut verse: Verse = Verse::new();

        // Create a vector to return
        let mut poem: Self = Poem::new();

        // Keep track of the last rune
        let mut last = Rune::None;

        // Keep track of the channel
        let mut channel: Option<Rune> = None;

        // Keep track of the line
        let mut j = 0;

        // Keep track of the column
        let mut i = 0;

        // Loop through every char in the iterator
        loop {
            // Get the next character, and unwrap it
            let c = chars.next();
            let c = match c {
                Some(c) => c,
                None => {
                    // Check for IO parse errors
                    if last == Rune::Read || last == Rune::Write || last == Rune::Addendum {
                        return Err(Mishap::IOMishap(j, i, ' '));
                    }

                    // If c is none, it indicates the end of a poem, so wrap up and
                    // then break from the loop
                    verse.add(&mut word, channel);

                    // Throw an error if the verse is empty
                    if verse.is_empty() && (last == Rune::Couplet || last == Rune::And) {
                        return Err(Mishap::ParseMishap(j, i, ' '));
                    }

                    // Push the verse and break
                    poem.add(&mut verse, Rune::None, env)?;
                    // append!(poem, last, Rune::None, verse, env);
                    break;
                }
            };

            // Determine the meter based on the character
            let rune = match c {
                ' ' => Rune::Pause,
                '/' => Rune::Path,
                '#' => Rune::Remark,
                '\'' | '"' => Rune::String,
                '`' => Rune::Poem,
                '<' => Rune::Read,
                '>' => next(&mut chars, &mut i, Rune::Write, vec![(">", Rune::Addendum)]),
                '1' => next(
                    &mut chars,
                    &mut i,
                    Rune::Else,
                    vec![(">", Rune::Write), (">>", Rune::Addendum)],
                ),
                '2' => next(
                    &mut chars,
                    &mut i,
                    Rune::Else,
                    vec![(">", Rune::Write2), (">>", Rune::Addendum2)],
                ),
                '|' => Rune::Couplet,
                '&' => next(
                    &mut chars,
                    &mut i,
                    Rune::Quiet,
                    vec![
                        ("&", Rune::And),
                        (">", Rune::WriteAll),
                        (">>", Rune::AddendumAll),
                    ],
                ),
                ';' => Rune::Continue,
                '\n' => {
                    j += 1;
                    i = 0;
                    Rune::Continue
                }
                '~' => Rune::Home,
                _ => Rune::Else,
            };

            // Some error checking, based on the last character
            match rune {
                Rune::Couplet
                | Rune::Quiet
                | Rune::And
                | Rune::Read
                | Rune::Write
                | Rune::Write2
                | Rune::WriteAll
                | Rune::Addendum
                | Rune::Addendum2
                | Rune::AddendumAll => {
                    if (last == Rune::Couplet
                        || last == Rune::Quiet
                        || last == Rune::And
                        || last == Rune::Read
                        || last == Rune::Write
                        || last == Rune::Write2
                        || last == Rune::WriteAll
                        || last == Rune::Addendum
                        || last == Rune::Addendum2
                        || last == Rune::AddendumAll)
                        || verse.is_empty()
                    {
                        return Err(Mishap::ParseMishap(j, i, c));
                    }
                }

                Rune::Continue => {
                    if last == Rune::Read
                        || last == Rune::Write
                        || last == Rune::Write2
                        || last == Rune::WriteAll
                        || last == Rune::Addendum
                        || last == Rune::Addendum2
                        || last == Rune::AddendumAll
                    {
                        return Err(Mishap::ParseMishap(j, i, c));
                    }
                }

                _ => {
                    if (last == Rune::Read
                        || last == Rune::Write
                        || last == Rune::Write2
                        || last == Rune::WriteAll
                        || last == Rune::Addendum
                        || last == Rune::Addendum2
                        || last == Rune::AddendumAll)
                        && rune == Rune::None
                        && rune == Rune::Read
                        && rune == Rune::Write
                        && rune == Rune::Write2
                        && rune == Rune::WriteAll
                        && rune == Rune::Addendum
                        && rune == Rune::Addendum2
                        && rune == Rune::AddendumAll
                        && rune == Rune::Couplet
                        && rune == Rune::Quiet
                        && rune == Rune::And
                        && rune == Rune::Continue
                    {
                        return Err(Mishap::IOMishap(j, i, c));
                    }
                }
            };

            // Do some action, based on the rune
            match rune {
                // Indicates the end of a word (space dilineated)
                Rune::Pause => {
                    verse.add(&mut word, channel);
                }

                Rune::Remark => {
                    remark!(chars);
                }

                // Indicates a string (' or ")
                Rune::String => {
                    string!(chars, j, i, c, word);
                    verse.add(&mut word, channel);
                }

                // Indicates a sub-poem
                Rune::Poem => {
                    poem!(chars, j, i, c, verse, word, env);
                }

                // Indicates a file operation (<, >, or >>)
                Rune::Read
                | Rune::Write
                | Rune::Write2
                | Rune::WriteAll
                | Rune::Addendum
                | Rune::Addendum2
                | Rune::AddendumAll => {
                    verse.add(&mut word, channel);
                    channel = Some(rune);
                    verse.io.push(rune);
                }

                // These meters indicate the end of a verse
                Rune::Couplet | Rune::Quiet | Rune::And | Rune::Continue => {
                    channel = None;
                    verse.add(&mut word, channel);
                    poem.add(&mut verse, rune, env)?;
                    // append!(poem, last, rune, verse, env);
                }

                // Interpret ~ as $HOME
                Rune::Home => {
                    let mut chars = env!("HOME").chars().collect();
                    word.append(&mut chars);
                }

                // Any other char i.e. Rune::Else
                _ => {
                    word.push(c);
                }
            }

            // Set the last meter
            if rune != Rune::Pause {
                last = rune;
            }

            // Increment i, but don't drift over newlines
            if c != '\n' {
                i += 1;
            }
        }

        // Return the poem
        Ok(poem)
    }
}