use directories::ProjectDirs;
use errors::*;
use std::borrow::Cow;
use std::collections::BTreeMap;
use std::fs::{self, File};
use std::path::{Path, PathBuf};
use syntect::dumps::{dump_to_file, from_binary, from_reader};
use syntect::highlighting::{Theme, ThemeSet};
use syntect::parsing::{SyntaxDefinition, SyntaxSet};

#[cfg(unix)]
use std::os::unix::fs::FileTypeExt;

lazy_static! {
    static ref PROJECT_DIRS: ProjectDirs =
        ProjectDirs::from("", "", crate_name!()).expect("Could not get home directory");
}

pub const BAT_THEME_DEFAULT: &str = "Monokai Extended";

pub struct HighlightingAssets {
    pub syntax_set: SyntaxSet,
    pub theme_set: ThemeSet,
}

impl HighlightingAssets {
    pub fn new() -> Self {
        Self::from_cache().unwrap_or_else(|_| Self::from_binary())
    }

    fn empty() -> Self {
        let mut syntax_set = SyntaxSet::new();
        syntax_set.load_plain_text_syntax();

        let theme_set = ThemeSet {
            themes: BTreeMap::new(),
        };
        HighlightingAssets {
            syntax_set,
            theme_set,
        }
    }

    pub fn from_files(dir: Option<&Path>, start_empty: bool) -> Result<Self> {
        let source_dir = dir.unwrap_or_else(|| PROJECT_DIRS.config_dir());

        let mut assets = if start_empty {
            Self::empty()
        } else {
            Self::from_binary_unlinked()
        };

        let theme_dir = source_dir.join("themes");

        let res = extend_theme_set(&mut assets.theme_set, &theme_dir);
        if !res.is_ok() {
            println!(
                "No themes were found in '{}', using the default set",
                theme_dir.to_string_lossy()
            );
        }

        let syntax_dir = source_dir.join("syntaxes");
        if syntax_dir.exists() {
            assets.syntax_set.load_syntaxes(syntax_dir, true)?;
        } else {
            println!(
                "No syntaxes were found in '{}', using the default set.",
                syntax_dir.to_string_lossy()
            );
        }

        Ok(assets)
    }

    fn from_cache() -> Result<Self> {
        let theme_set_path = theme_set_path();
        let syntax_set_file = File::open(&syntax_set_path()).chain_err(|| {
            format!(
                "Could not load cached syntax set '{}'",
                syntax_set_path().to_string_lossy()
            )
        })?;
        let mut syntax_set: SyntaxSet =
            from_reader(syntax_set_file).chain_err(|| "Could not parse cached syntax set")?;
        syntax_set.link_syntaxes();

        let theme_set_file = File::open(&theme_set_path).chain_err(|| {
            format!(
                "Could not load cached theme set '{}'",
                theme_set_path.to_string_lossy()
            )
        })?;
        let theme_set: ThemeSet =
            from_reader(theme_set_file).chain_err(|| "Could not parse cached theme set")?;

        Ok(HighlightingAssets {
            syntax_set,
            theme_set,
        })
    }

    fn from_binary_unlinked() -> Self {
        let syntax_set: SyntaxSet = from_binary(include_bytes!("../assets/syntaxes.bin"));
        let theme_set: ThemeSet = from_binary(include_bytes!("../assets/themes.bin"));

        HighlightingAssets {
            syntax_set,
            theme_set,
        }
    }

    fn from_binary() -> Self {
        let mut assets = Self::from_binary_unlinked();
        assets.syntax_set.link_syntaxes();
        assets
    }

    pub fn save(&self, dir: Option<&Path>) -> Result<()> {
        let target_dir = dir.unwrap_or_else(|| PROJECT_DIRS.cache_dir());
        let _ = fs::create_dir(target_dir);
        let theme_set_path = target_dir.join("themes.bin");
        let syntax_set_path = target_dir.join("syntaxes.bin");

        print!(
            "Writing theme set to {} ... ",
            theme_set_path.to_string_lossy()
        );
        dump_to_file(&self.theme_set, &theme_set_path).chain_err(|| {
            format!(
                "Could not save theme set to {}",
                theme_set_path.to_string_lossy()
            )
        })?;
        println!("okay");

        print!(
            "Writing syntax set to {} ... ",
            syntax_set_path.to_string_lossy()
        );
        dump_to_file(&self.syntax_set, &syntax_set_path).chain_err(|| {
            format!(
                "Could not save syntax set to {}",
                syntax_set_path.to_string_lossy()
            )
        })?;
        println!("okay");

        Ok(())
    }

    pub fn get_theme(&self, theme: &str) -> &Theme {
        match self.theme_set.themes.get(theme) {
            Some(theme) => theme,
            None => {
                use ansi_term::Colour::Yellow;
                eprintln!(
                    "{}: Unknown theme '{}', using default.",
                    Yellow.paint("[bat warning]"),
                    theme
                );
                &self.theme_set.themes[BAT_THEME_DEFAULT]
            }
        }
    }

    pub fn get_syntax(&self, language: Option<&str>, filename: Option<&str>) -> &SyntaxDefinition {
        let syntax = match (language, filename) {
            (Some(language), _) => self.syntax_set.find_syntax_by_token(language),
            (None, Some(filename)) => {
                #[cfg(not(unix))]
                let may_read_from_file = true;

                // Do not peek at the file (to determine the syntax) if it is a FIFO because they can
                // only be read once.
                #[cfg(unix)]
                let may_read_from_file = !fs::metadata(filename)
                    .map(|m| m.file_type().is_fifo())
                    .unwrap_or(false);

                if may_read_from_file {
                    self.syntax_set
                        .find_syntax_for_file(filename)
                        .unwrap_or(None)
                } else {
                    None
                }
            }
            (None, None) => None,
        };

        syntax.unwrap_or_else(|| self.syntax_set.find_syntax_plain_text())
    }
}

// TODO: ideally, this function would be part of syntect's `ThemeSet`.
fn extend_theme_set<P: AsRef<Path>>(theme_set: &mut ThemeSet, folder: P) -> Result<()> {
    let paths = ThemeSet::discover_theme_paths(folder)?;
    for p in &paths {
        let theme = ThemeSet::get_theme(p)?;
        let basename = p
            .file_stem()
            .and_then(|x| x.to_str())
            .ok_or("Could not get theme basename")?;
        theme_set.themes.insert(basename.to_owned(), theme);
    }

    Ok(())
}

fn theme_set_path() -> PathBuf {
    PROJECT_DIRS.cache_dir().join("themes.bin")
}

fn syntax_set_path() -> PathBuf {
    PROJECT_DIRS.cache_dir().join("syntaxes.bin")
}

pub fn config_dir() -> Cow<'static, str> {
    PROJECT_DIRS.config_dir().to_string_lossy()
}

pub fn clear_assets() {
    print!("Clearing theme set cache ... ");
    fs::remove_file(theme_set_path()).ok();
    println!("okay");

    print!("Clearing syntax set cache ... ");
    fs::remove_file(syntax_set_path()).ok();
    println!("okay");
}