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

lazy_static! {
    static ref PROJECT_DIRS: ProjectDirs = ProjectDirs::from("", "", crate_name!());
}

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())
    }

    pub fn from_files() -> Result<Self> {
        let config_dir = PROJECT_DIRS.config_dir();

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

        let theme_set = ThemeSet::load_from_folder(&theme_dir).map_err(|_| {
            io::Error::new(
                io::ErrorKind::Other,
                format!(
                    "Could not load themes from '{}'",
                    theme_dir.to_string_lossy()
                ),
            )
        })?;

        let mut syntax_set = SyntaxSet::new();
        let syntax_dir = config_dir.join("syntax");
        let _ = syntax_set.load_syntaxes(syntax_dir, true);
        syntax_set.load_plain_text_syntax();

        Ok(HighlightingAssets {
            syntax_set,
            theme_set,
        })
    }

    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).map_err(|_| {
            io::Error::new(io::ErrorKind::Other, "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)
            .map_err(|_| io::Error::new(io::ErrorKind::Other, "Could not parse cached theme set"))?;

        Ok(HighlightingAssets {
            syntax_set,
            theme_set,
        })
    }

    fn from_binary() -> Self {
        let mut syntax_set: SyntaxSet = from_binary(include_bytes!("../assets/syntax_set"));
        syntax_set.link_syntaxes();
        let theme_set: ThemeSet = from_binary(include_bytes!("../assets/theme_set"));

        HighlightingAssets {
            syntax_set,
            theme_set,
        }
    }

    pub fn save(&self) -> Result<()> {
        let cache_dir = PROJECT_DIRS.cache_dir();
        let _ = fs::create_dir(cache_dir);
        let theme_set_path = theme_set_path();
        let syntax_set_path = syntax_set_path();

        print!(
            "Writing theme set to {} ... ",
            theme_set_path.to_string_lossy()
        );
        dump_to_file(&self.theme_set, &theme_set_path).map_err(|_| {
            io::Error::new(
                io::ErrorKind::Other,
                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).map_err(|_| {
            io::Error::new(
                io::ErrorKind::Other,
                format!(
                    "Could not save syntax set to {}",
                    syntax_set_path.to_string_lossy()
                ),
            )
        })?;
        println!("okay");

        Ok(())
    }

    pub fn default_theme(&self) -> Result<&Theme> {
        Ok(self.theme_set
            .themes
            .get("Default")
            .ok_or_else(|| io::Error::new(io::ErrorKind::Other, "Could not find 'Default' theme"))?)
    }
}

pub fn theme_set_path() -> PathBuf {
    PROJECT_DIRS.cache_dir().join("theme_set")
}

pub fn syntax_set_path() -> PathBuf {
    PROJECT_DIRS.cache_dir().join("syntax_set")
}

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