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

use super::{
    error::{Error, Result},
    kvstore,
    minemod::ModId,
};

/// Represents an on-disk Minetest world.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct World {
    path: PathBuf,
}

impl World {
    pub fn open<P: AsRef<Path>>(path: P) -> Result<World> {
        World::open_path(path.as_ref())
    }

    fn open_path(path: &Path) -> Result<World> {
        let conf = path.join("world.mt");
        if !conf.is_file() {
            return Err(Error::InvalidWorldDir(path.into()));
        }

        Ok(World { path: path.into() })
    }

    fn conf(&self) -> Result<HashMap<String, String>> {
        let conf = self.path.join("world.mt");
        kvstore::read(&conf)
    }

    /// Returns the name of the world.
    pub fn world_name(&self) -> Result<String> {
        let fallback = self
            .path
            .file_name()
            .map(|s| s.to_str().expect("Non-UTF8 directory encountered"));

        let conf = self.conf()?;
        conf.get("world_name")
            .map(String::as_str)
            .or(fallback)
            .ok_or_else(|| Error::InvalidWorldDir(self.path.clone()))
            .map(Into::into)
    }

    /// Extract the game that this world uses.
    pub fn game_id(&self) -> Result<String> {
        let conf = self.conf()?;
        conf.get("gameid").ok_or(Error::NoGameSet).map(Into::into)
    }

    /// Returns all mods that are loaded in this world.
    ///
    /// This returns mods that are explicitely loaded in the config, but not mods that are loaded
    /// through the game.
    pub fn mods(&self) -> Result<Vec<ModId>> {
        let conf = self.conf()?;
        const PREFIX_LEN: usize = "load_mod_".len();
        Ok(conf
            .iter()
            .filter(|(k, _)| k.starts_with("load_mod_"))
            .filter(|(_, v)| *v == "true")
            .map(|i| i.0[PREFIX_LEN..].into())
            .collect())
    }

    /// Enable the given mod.
    ///
    /// Note that this function does not ensure that the mod exists on-disk, nor does it do any
    /// dependency checks. It simply adds the right `load_mod`-line to the world configuration
    /// file.
    pub fn enable_mod(&self, mod_id: &str) -> Result<()> {
        let mut conf = self.conf()?;
        let key = format!("load_mod_{}", mod_id);
        conf.entry(key)
            .and_modify(|e| *e = "true".into())
            .or_insert_with(|| "true".into());
        kvstore::write(&conf, &self.path.join("world.mt"))
    }
}

impl fmt::Display for World {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.world_name().map_err(|_| fmt::Error)?)
    }
}