use crate::error::ParsePresetError;
use crate::parse::{Span, Token};
use crate::{FilterMode, ScaleFactor, ScaleType, Scaling, WrapMode};
use nom::bytes::complete::tag;
use nom::character::complete::digit1;
use nom::combinator::{eof, map_res};
use nom::error::Error;
use nom::IResult;
use std::collections::HashMap;
use std::fs::File;
use std::io::Read;
use std::path::{Path, PathBuf};
use std::str::FromStr;

#[derive(Debug)]
pub enum Value {
    ShaderCount(i32),
    Shader(i32, PathBuf),
    ScaleX(i32, ScaleFactor),
    ScaleY(i32, ScaleFactor),
    Scale(i32, ScaleFactor),
    ScaleType(i32, ScaleType),
    FilterMode(i32, FilterMode),
    FloatFramebuffer(i32, bool),
    SrgbFramebuffer(i32, bool),
    MipmapInput(i32, bool),
    WrapMode(i32, WrapMode),
    Alias(String),
    Parameter(String, f32),
    TexturePath(String, FilterMode, bool, PathBuf),
}

fn from_int(input: Span) -> Result<i32, std::num::ParseIntError> {
    i32::from_str(*input)
}

fn parse_indexed_key<'a>(key: &'static str, input: Span<'a>) -> IResult<Span<'a>, i32> {
    let (input, _) = tag(key)(input)?;
    let (input, idx) = map_res(digit1, from_int)(input)?;
    let (input, _) = eof(input)?;
    Ok((input, idx))
}

pub const SHADER_MAX_REFERENCE_DEPTH: usize = 16;

fn load_child_reference_strings(
    mut root_references: Vec<PathBuf>,
    root_path: impl AsRef<Path>,
) -> Result<Vec<(PathBuf, String)>, ParsePresetError> {
    let root_path = root_path.as_ref();
    let mut reference_depth = 0;
    let mut reference_strings: Vec<(PathBuf, String)> = Vec::new();
    while let Some(reference_path) = root_references.pop() {
        if reference_depth > SHADER_MAX_REFERENCE_DEPTH {
            return Err(ParsePresetError::ExceededReferenceDepth);
        }
        let mut root_path = root_path.to_path_buf();
        root_path.push(reference_path);
        let mut reference_root = root_path
            .canonicalize()
            .map_err(|e| ParsePresetError::IOError(root_path, e))?;

        let mut reference_contents = String::new();
        File::open(&reference_root)
            .map_err(|e| ParsePresetError::IOError(reference_root.clone(), e))?
            .read_to_string(&mut reference_contents)
            .map_err(|e| ParsePresetError::IOError(reference_root.clone(), e))?;

        let mut new_tokens = super::do_lex(&reference_contents)?;
        let mut new_references: Vec<PathBuf> = new_tokens
            .drain_filter(|token| *token.key.fragment() == "#reference")
            .map(|value| PathBuf::from(*value.value.fragment()))
            .collect();

        root_references.append(&mut new_references);

        // return the relative root that shader and texture paths are to be resolved against.
        if !reference_root.is_dir() {
            reference_root.pop();
        }

        // trim end space
        reference_strings.push((reference_root, reference_contents));
    }

    Ok(reference_strings)
}

pub fn parse_preset(path: impl AsRef<Path>) -> Result<Vec<Value>, ParsePresetError> {
    let path = path.as_ref();
    let path = path.canonicalize()
        .map_err(|e| ParsePresetError::IOError(path.to_path_buf(), e))?;

    let mut contents = String::new();
    File::open(&path).and_then(|mut f| f.read_to_string(&mut contents))
        .map_err(|e| ParsePresetError::IOError(path.to_path_buf(), e))?;

    let tokens = super::token::do_lex(&contents)?;
    parse_values(tokens, path)
}

pub fn parse_values(
    mut tokens: Vec<Token>,
    root_path: impl AsRef<Path>,
) -> Result<Vec<Value>, ParsePresetError> {
    let mut root_path = root_path.as_ref().to_path_buf();
    if root_path.is_relative() {
        return Err(ParsePresetError::RootPathWasNotAbsolute);
    }
    if !root_path.is_dir() {
        // we don't really care if this doesn't do anything because a non-canonical root path will
        // fail at a later stage during resolution.
        root_path.pop();
    }

    let references: Vec<PathBuf> = tokens
        .drain_filter(|token| *token.key.fragment() == "#reference")
        .map(|value| PathBuf::from(*value.value.fragment()))
        .collect();

    // unfortunately we need to lex twice because there's no way to know the references ahead of time.
    let child_strings = load_child_reference_strings(references, &root_path)?;
    let mut all_tokens: Vec<(&Path, Vec<Token>)> = Vec::new();
    all_tokens.push((root_path.as_path(), tokens));

    for (path, string) in child_strings.iter() {
        let mut tokens = crate::parse::do_lex(string.as_ref())?;
        tokens.retain(|token| *token.key.fragment() != "#reference");
        all_tokens.push((path.as_path(), tokens))
    }

    // collect all possible parameter names.
    let mut parameter_names: Vec<&str> = Vec::new();
    for (_, tokens) in all_tokens.iter_mut() {
        for token in tokens.drain_filter(|token| *token.key.fragment() == "parameters") {
            let parameter_name_string: &str = *token.value.fragment();
            for parameter_name in parameter_name_string.split(";") {
                parameter_names.push(parameter_name);
            }
        }
    }

    // collect all possible texture names.
    let mut texture_names: Vec<&str> = Vec::new();
    for (_, tokens) in all_tokens.iter_mut() {
        for token in tokens.drain_filter(|token| *token.key.fragment() == "textures") {
            let texture_name_string: &str = *token.value.fragment();
            for texture_name in texture_name_string.split(";") {
                texture_names.push(texture_name);
            }
        }
    }

    let mut values = Vec::new();
    // resolve shader paths.
    for (ref path, tokens) in all_tokens.iter_mut() {
        for token in tokens.drain_filter(|token| parse_indexed_key("shader", token.key).is_ok()) {
            let (_, index) = parse_indexed_key("shader", token.key).map_err(|e| match e {
                nom::Err::Error(e) | nom::Err::Failure(e) => {
                    let input: Span = e.input;
                    ParsePresetError::ParserError {
                        offset: input.location_offset(),
                        row: input.location_line(),
                        col: input.get_column(),
                    }
                }
                _ => ParsePresetError::ParserError {
                    offset: 0,
                    row: 0,
                    col: 0,
                },
            })?;

            let mut relative_path = path.to_path_buf();
            relative_path.push(*token.value.fragment());
            relative_path
                .canonicalize()
                .map_err(|e| ParsePresetError::IOError(relative_path.clone(), e))?;
            values.push(Value::Shader(index, relative_path))
        }
    }

    // resolve texture paths
    let mut textures = Vec::new();
    for (ref path, tokens) in all_tokens.iter_mut() {
        for token in tokens.drain_filter(|token|
            texture_names.contains(token.key.fragment())
        ) {
            let mut relative_path = path.to_path_buf();
            relative_path.push(*token.value.fragment());
            relative_path
                .canonicalize()
                .map_err(|e| ParsePresetError::IOError(relative_path.clone(), e))?;
            textures.push((token.key, relative_path))
        }
    }

    let tokens: Vec<Token> = all_tokens
        .into_iter()
        .flat_map(|(_, token)| token)
        .collect();
    // all tokens should be ok to process now.
    Ok(values)
}

#[cfg(test)]
mod test {
    use std::path::PathBuf;
    use crate::parse::value::parse_preset;

    #[test]
    pub fn parse_basic() {
        let root = PathBuf::from("test/slang-shaders/bezel/Mega_Bezel/Presets/MBZ__5__POTATO.slangp");
        let basic = parse_preset(&root);
        eprintln!("{:?}", basic);
    }
}