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

#[derive(Debug, PartialEq, Eq)]
pub enum Mishap {
    ParseMishap(usize, usize, char),
    IOMishap(usize, usize, char),
    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, last: Rune);
}

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. Also sets the meter of the [Verse].
    fn add(&mut self, verse: &mut Self::Type, last: Rune, meter: Rune) {
        if !verse.is_empty() {
            verse.meter = meter;
            if last == Rune::Couplet || meter == Rune::Couplet {
                verse.couplet = true;
            }
            self.push(verse.clone());
            verse.clear();
        }
    }
}

/// A [Poem] can parse poetry
pub trait Readable {
    fn read(poetry: String) -> 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, [Poem::read] may
    /// return a [Mishap]. See [Poem::recite][super::recite] for how each
    /// [Verse] in a [Poem] is called.
    fn read(poetry: String) -> 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 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);

                    // 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, last, Rune::None);
                    break;
                }
            };

            // Determine the meter based on the character
            let rune = match c {
                ' ' => Rune::Pause,
                '/' => Rune::Path,
                '#' => Rune::Remark,
                '\'' | '"' => Rune::String,
                '`' => Rune::Poem,
                '<' => {
                    verse.couplet = true;
                    Rune::Read
                }
                '>' => next!(chars, i, Rune::Write, Rune::Addendum, '>'),
                '|' => Rune::Couplet,
                '&' => next!(chars, i, Rune::Quiet, Rune::And, '&'),
                ';' => 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::Addendum => {
                    if (last == Rune::Couplet
                        || last == Rune::Quiet
                        || last == Rune::And
                        || last == Rune::Read
                        || last == Rune::Write
                        || last == Rune::Addendum)
                        || verse.is_empty()
                    {
                        return Err(Mishap::ParseMishap(j, i, c));
                    }
                }

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

                _ => {
                    if (last == Rune::Read || last == Rune::Write || last == Rune::Addendum)
                        && rune == Rune::None
                        && rune == Rune::Read
                        && rune == Rune::Write
                        && rune == Rune::Addendum
                        && 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);
                }

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

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

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

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

                // These meters indicate the end of a verse
                Rune::Couplet | Rune::Quiet | Rune::And | Rune::Continue => {
                    verse.add(&mut word);
                    poem.add(&mut verse, last, rune);
                }

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

                // Any other char i.e. Meter::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)
    }
}