use std::error::Error;
use std::fs::File;
use std::io::{Read, Write};
use std::path::{Path, PathBuf};
use tile_source::TileSource;
use toml::Value;
use xdg;

static DEFAULT_CONFIG: &'static str = include_str!("../default_config.toml");


#[derive(Debug)]
pub struct Config {
    tile_cache_dir: PathBuf,
    sources: Vec<(String, TileSource)>,
    fps: f64,
}

impl Config {
    pub fn load() -> Result<Config, String> {
        if let Ok(xdg_dirs) = xdg::BaseDirectories::with_prefix("deltamap") {
            if let Some(config_path) = xdg_dirs.find_config_file("config.toml") {
                info!("load config from path {:?}", config_path);

                Config::from_toml_file(config_path)
            } else {
                // try to write a default config file
                if let Ok(path) = xdg_dirs.place_config_file("config.toml") {
                    if let Ok(mut file) = File::create(&path) {
                        if file.write_all(DEFAULT_CONFIG.as_bytes()).is_ok() {
                            info!("write default config to {:?}", &path);
                        }
                    }
                }

                Config::from_toml_str(DEFAULT_CONFIG)
            }
        } else {
            info!("load default config");
            Config::from_toml_str(DEFAULT_CONFIG)
        }
    }

    /// Returns a tile cache directory path at a standard XDG cache location. The returned path may
    /// not exist.
    fn default_tile_cache_dir() -> Result<PathBuf, String> {
        let xdg_dirs = xdg::BaseDirectories::with_prefix("deltamap")
            .map_err(|e| e.description().to_string())?;

        match xdg_dirs.find_cache_file("tiles") {
            Some(dir) => Ok(dir),
            None => Ok(xdg_dirs.get_cache_home().join("tiles")),
        }
    }

    pub fn from_toml_str(toml_str: &str) -> Result<Config, String> {
        match toml_str.parse::<Value>() {
            Ok(Value::Table(ref table)) => {
                let tile_cache_dir = {
                    match table.get("tile_cache_dir") {
                        Some(dir) => {
                            PathBuf::from(
                                dir.as_str()
                                   .ok_or_else(|| "tile_cache_dir has to be a string".to_string())?
                            )
                        },
                        None => Config::default_tile_cache_dir()?,
                    }
                };

                let fps = {
                    match table.get("fps") {
                        Some(&Value::Float(fps)) => fps,
                        Some(&Value::Integer(fps)) => fps as f64,
                        Some(_) => return Err("fps has to be an integer or a float.".to_string()),
                        None => 60.0,
                    }
                };

                let sources_table = table.get("tile_sources")
                    .ok_or_else(|| "missing \"tile_sources\" table".to_string())?
                    .as_table()
                    .ok_or_else(|| "\"tile_sources\" has to be a table".to_string())?;

                let mut sources_vec: Vec<(String, TileSource)> = Vec::with_capacity(sources_table.len());

                for (id, (name, source)) in sources_table.iter().enumerate() {
                    let min_zoom = source.get("min_zoom")
                        .unwrap_or_else(|| &Value::Integer(0))
                        .as_integer()
                        .ok_or_else(|| "min_zoom has to be an integer".to_string())
                        .and_then(|m| {
                            if m < 0 || m > 30 {
                                Err(format!("min_zoom = {} is out of bounds, has to be in interval [0, 30]", m))
                            } else {
                                Ok(m)
                            }
                        })?;

                    let max_zoom = source.get("max_zoom")
                        .ok_or_else(|| format!("source {:?} is missing \"max_zoom\" entry", name))?
                        .as_integer()
                        .ok_or_else(|| "max_zoom has to be an integer".to_string())
                        .and_then(|m| {
                            if m < 0 || m > 30 {
                                Err(format!("max_zoom = {} is out of bounds, has to be in interval [0, 30]", m))
                            } else {
                                Ok(m)
                            }
                        })?;

                    if min_zoom > max_zoom {
                        warn!("min_zoom ({}) and max_zoom ({}) allow no valid tiles", min_zoom, max_zoom);
                    } else if min_zoom == max_zoom {
                        warn!("min_zoom ({}) and max_zoom ({}) allow only one zoom level", min_zoom, max_zoom);
                    }

                    let url_template = source.get("url_template")
                        .ok_or_else(|| format!("source {:?} is missing \"url_template\" entry", name))?
                        .as_str()
                        .ok_or_else(|| "url_template has to be a string".to_string())?;

                    let extension = source.get("extension")
                        .ok_or_else(|| format!("source {:?} is missing \"extension\" entry", name))?
                        .as_str()
                        .ok_or_else(|| "extension has to be a string".to_string())?;

                    if name.contains('/') || name.contains('\\') {
                        return Err(format!("source name ({:?}) must not contain slashes (\"/\" or \"\\\")", name));
                    }

                    let mut path = PathBuf::from(&tile_cache_dir);
                    path.push(name);

                    sources_vec.push((
                        name.clone(),
                        TileSource::new(
                            id as u32,
                            url_template.to_string(),
                            path,
                            extension.to_string(),
                            min_zoom as u32,
                            max_zoom as u32,
                        ),
                    ));
                }

                Ok(
                    Config {
                        tile_cache_dir: tile_cache_dir,
                        sources: sources_vec,
                        fps: fps,
                    }
                )
            },
            Ok(_) => Err("TOML file has invalid structure. Expected a Table as the top-level element.".to_string()),
            Err(e) => Err(e.description().to_string()),
        }
    }

    pub fn from_toml_file<P: AsRef<Path>>(path: P) -> Result<Config, String> {
        let mut file = File::open(path).map_err(|e| e.description().to_string())?;

        let mut content = String::new();
        file.read_to_string(&mut content).map_err(|e| e.description().to_string())?;

        Config::from_toml_str(&content)
    }

    pub fn tile_sources(&self) -> &[(String, TileSource)] {
        &self.sources
    }

    pub fn fps(&self) -> f64 {
        self.fps
    }
}

#[cfg(test)]
mod tests {
    use config::*;

    #[test]
    fn default_config() {
        assert!(Config::from_toml_str(DEFAULT_CONFIG).is_ok())
    }
}