use std::collections::HashMap;
use std::fs;
use std::io;
use std::path::{Path, PathBuf};

use structopt::StructOpt;
use serde::{Serialize, Deserialize};
use tera::{Tera, Filter, Value};

const TMPL_FILES: &'static [&'static str] = &["index.html"];

#[derive(Debug, StructOpt, Serialize)]
#[structopt(name = "gallery")]
pub struct Options {
    #[structopt(long, help = "Just a thing")]
    pub check: bool,
    #[structopt(short, long, help = "Config file location")]
    pub config: Option<PathBuf>,
    #[structopt(help = "Picture location")]
    pub load: PathBuf,
    #[structopt(short, long, default_value = "png", help = "Image extension to use for converted files")]
    pub ext: String,
    #[structopt(long, short, default_value = "build", help = "Where to build site")]
    pub builddir: PathBuf,

    #[structopt(long, help = "Full size url prefix")]
    pub url_prefix: Option<String>,
}

#[derive(Debug, thiserror::Error)]
pub enum ConfigError {
    #[error("reading from file")]
    Reading {
        #[from]
        source: io::Error,
    },
    #[error("parsing config file")]
    Parsing {
        #[from]
        source: serde_yaml::Error,
    },
    #[error("compiling glob pattern")]
    CompilePattern {
        #[from]
        source: glob::PatternError,
    },
    #[error("compiling templates")]
    CompileTemplate {
        #[from]
        source: tera::Error,
    },
}

#[derive(Deserialize, Debug, Serialize)]
pub struct Config {
    pub imageglob: String,
    pub info: HashMap<String, String>,
    pub sizes: HashMap<String, u32>,

    #[serde(skip)]
    pub imageglob_compiled: glob::Pattern,
}

struct ReltoFilter {
    dir: PathBuf,
}

#[derive(Debug)]
pub struct Context {
    pub options: Options,
    pub config: Config,
    pub imgdir: PathBuf,

    pub tmpl: Tera,
}

impl Context {
    pub fn new_with_args() -> Result<Context, ConfigError> {
        let opts = Options::from_args();
        let config = Config::load_with_options(&opts)?;
        let imgdir = opts.builddir.join("imgs");

        // Create img dir
        if let Err(err) = fs::create_dir(&imgdir) {
            if err.kind() != io::ErrorKind::AlreadyExists {
                return Err(ConfigError::from(err));
            }
        }

        // Compile templates
        let mut tera = Tera::default();
        let tmpl_dir = opts.load.join("templates");
        TMPL_FILES.iter().map(|fname| -> Result<(), ConfigError> {
            let path = tmpl_dir.join(fname);
            tera.add_template_file(path, Some(fname))?;
            Ok(())
        }).collect::<Result<(), ConfigError>>()?;

        tera.register_filter("relto_build", ReltoFilter::new(&opts.builddir));

        Ok(Context {
            options: opts,
            config: config,
            imgdir: imgdir,
            tmpl: tera,
        })
    }

    pub fn get_image_files(&self) -> Result<Vec<PathBuf>, io::Error> {
        let files = fs::read_dir(&self.options.load)?
            // Remove errored entries (SILENTLY)
            .filter(|entry| entry.is_ok())
            .map(|entry| entry.unwrap().path())
            // Filter out directories and files that do not match pattern
            .filter(|path| path.file_name()
                    .map_or(false, |file| self.config.imageglob_compiled.matches(file.to_str().unwrap()))
                    )
            .collect();

        Ok(files)
    }
}

impl ReltoFilter {
    pub fn new(dir: &Path) -> Self {
        ReltoFilter {
            dir: dir.to_path_buf(),
        }
    }
}

impl Filter for ReltoFilter {
    fn filter(&self, value: &Value, _: &HashMap<String, tera::Value>) -> tera::Result<Value> {
        if let Value::String(path) = value {
            let path = PathBuf::from(path);
            match path.strip_prefix(&self.dir) {
                Ok(relto) => Ok(Value::String(relto.to_string_lossy().to_string())),
                Err(err) => Err(tera::Error::call_filter("relto", err)),
            }
        } else {
            Err(tera::Error::msg("Input to relto filter must be string"))
        }
    }
}

impl Config {
    fn load_from_file(path: &PathBuf) -> Result<Config, ConfigError> {
        let content = fs::read_to_string(path)?;
        let mut config: Config = serde_yaml::from_str(&content)?;

        config.imageglob_compiled = glob::Pattern::new(&config.imageglob)?;

        Ok(config)
    }

    pub fn load_with_options(opts: &Options) -> Result<Config, ConfigError> {
        let config_path = match &opts.config {
            Some(path) => path.to_path_buf(),
            None => opts.load.join("imginfo.yml"),
        };

        Config::load_from_file(&config_path)
    }


}