mod constants;
mod version;
mod profile;
mod strsub;
mod download;

use std::borrow::Cow;
use std::collections::HashMap;
use std::env::consts::{ARCH, OS};
use std::error::Error;
use std::fmt::{Display, Formatter};
use std::io::ErrorKind;
use std::path::{Path, PathBuf};
use const_format::formatcp;
use futures::TryFutureExt;
use log::{debug, warn};
use serde::{Deserialize, Serialize};
use sha1_smol::Sha1;
use sysinfo::System;
use tokio::fs::File;
use tokio::{fs, io};
use tokio::io::AsyncReadExt;
use version::VersionList;
use profile::{Instance, Profile};
use crate::launcher::download::{Download, VerifiedDownload};
use crate::launcher::version::{VersionResolveError, VersionResult};
use crate::version::{DownloadInfo, Library, OSRestriction, OperatingSystem};

#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct Settings {
    profiles: HashMap<String, Profile>,
    instances: HashMap<String, Instance>
}

#[derive(Debug)]
enum SettingsLoadError {
    IO(io::Error),
    Format(serde_json::Error)
}

impl Display for SettingsLoadError {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match self {
            SettingsLoadError::IO(err) => write!(f, "I/O error loading settings: {}", err),
            SettingsLoadError::Format(err) => write!(f, "settings format error: {}", err),
        }
    }
}

impl Error for SettingsLoadError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        match self {
            SettingsLoadError::IO(err) => Some(err),
            SettingsLoadError::Format(err) => Some(err),
        }
    }
}

impl Settings {
    async fn load(path: impl AsRef<Path>) -> Result<Settings, SettingsLoadError> {
        let data = match fs::read_to_string(&path).await {
            Ok(data) => data,
            Err(e) => return match e.kind() {
                ErrorKind::NotFound => Ok(Settings::default()),
                _ => Err(SettingsLoadError::IO(e))
            }
        };

        serde_json::from_str(data.as_str()).map_err(SettingsLoadError::Format)
    }
}

struct SystemInfo {
    os: OperatingSystem,
    os_version: String,
    arch: String
}

struct LibraryRepository {
    home: PathBuf
}

pub struct Launcher {
    online: bool,
    home: PathBuf,
    versions: VersionList,
    
    settings_path: PathBuf, // maybe redundant but idc >:3
    settings: Settings,

    system_info: SystemInfo,

    libraries: LibraryRepository
}

#[derive(Debug)]
pub enum LaunchError {
    UnknownVersion(String),
    LoadVersion(Box<dyn Error>),
    ResolveVersion(VersionResolveError)
}

impl Display for LaunchError {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match &self {
            LaunchError::UnknownVersion(id) => write!(f, "unknown version id: {id}"),
            LaunchError::LoadVersion(e) => write!(f, "error loading remote version: {e}"),
            LaunchError::ResolveVersion(e) => write!(f, "error resolving remote version: {e}")
        }
    }
}

impl Error for LaunchError {
    fn cause(&self) -> Option<&dyn Error> {
        match &self {
            LaunchError::LoadVersion(e) => Some(e.as_ref()),
            LaunchError::ResolveVersion(e) => Some(e),
            _ => None
        }
    }
}

impl Launcher {
    // FIXME: more descriptive error type por favor
    pub async fn new(home: &Path, online: bool) -> Result<Launcher, Box<dyn Error>> {
        let home = home.to_owned();
        let versions_home = home.join("versions");
        let versions;

        match tokio::fs::create_dir_all(&home).await {
            Ok(_) => (),
            Err(e) => match e.kind() {
                ErrorKind::AlreadyExists => (),
                _ => {
                    warn!("Failed to create launcher home directory: {}", e);
                    return Err(e.into());
                }
            }
        }

        debug!("Version list online?: {online}");
        if online {
            versions = VersionList::online(versions_home.as_ref()).await?;
        } else {
            versions = VersionList::offline(versions_home.as_ref()).await?;
        }
        
        let settings_path = home.join("ozone.json");
        let settings = Settings::load(&settings_path).await?;

        Ok(Launcher {
            online,
            home: home.to_owned(),
            versions,
            settings_path,
            settings,
            system_info: SystemInfo::new(),
            libraries: LibraryRepository {
                home: home.join("libraries"),
            }
        })
    }

    pub async fn prepare_launch(&self, profile: &Profile) -> Result<(), LaunchError> {
        /* tasks 2 l;aunch the gayme!!!! :3
         *  - java runtime
         *    - normal process (good research, past figboot :3)
         *  - libraries
         *    - check which libraries we actually need (some have classifiers that don't apply to us)
         *    - of the libraries we need, check which have correct size and sha1
         *    - redownload necessary libraries
         *      - (if offline mode and there are libraries to download, then explode violently)
         *    - extract natives
         *  - logging
         *    - download the config if present and necessary
         *      - (explode if offline mode and we need to download stuff)
         *  - assets
         *    - get asset index (check if our local copy is good and redownload if not)
         *    - check what ones are good and what needs to be downloaded
         *    - download them
         *      - (if offline mode, explode)
         *    - if virtual or resource-mapped, copy (or perhaps hardlink? that would be cool)
         *  - the actual client jar
         *    - check integriddy and download if needed
         *      - (explode if offline mode)
         *  - launch the game
         *    - build argument list and whatnot also
         */
        let ver_res = self.versions.get_version_lazy(&profile.version_id);
        let ver = match ver_res {
            VersionResult::Remote(mv) => Cow::Owned(self.versions.load_remote_version(mv).await.map_err(|e| LaunchError::LoadVersion(e))?),
            VersionResult::Complete(cv) => Cow::Borrowed(cv),
            VersionResult::None => {
                return Err(LaunchError::UnknownVersion(profile.version_id.clone()).into())
            }
        };

        let ver = self.versions.resolve_version(ver.as_ref()).await.map_err(|e| LaunchError::ResolveVersion(e))?;

        // todo: make a list of all the required libraries

        todo!()
    }
}

#[derive(Debug, Clone)]
enum LibraryError {
    InvalidName(String),
    IOError(ErrorKind)
}

impl Display for LibraryError {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match self {
            LibraryError::InvalidName(name) => write!(f, "invalid name: {name}"),
            LibraryError::IOError(e) => write!(f, "io error reading library: {e}"),
        }
    }
}

impl Error for LibraryError {}

const ARCH_BITS: &'static str = formatcp!("{}", usize::BITS);

impl LibraryRepository {
    fn lib_replace(key: &str) -> Option<Cow<'static, str>> {
        match key {
            "arch" => Some(Cow::Borrowed(ARCH_BITS)),
            _ => None
        }
    }

    fn get_artifact_base_dir(name: &str) -> Option<PathBuf> {
        let end_of_gid = name.find(':')?;

        Some(name[..end_of_gid].split('.').chain(name.split(':').skip(1).take(2)).collect())
    }

    fn get_artifact_filename(name: &str, classifier: Option<&str>) -> Option<PathBuf> {
        let n: Vec<&str> = name.splitn(4, ':').skip(1).collect();

        if let Some(classifier) = classifier {
            match n.len() {
                3 => Some(PathBuf::from(strsub::replace_thru(format!("{}-{}-{}.jar", n[1], n[2], classifier), Self::lib_replace))),
                4 => Some(PathBuf::from(strsub::replace_thru(format!("{}-{}-{}-{}.jar", n[1], n[2], classifier, n[3]), Self::lib_replace))),
                _ => None
            }
        } else {
            match n.len() {
                3 => Some(PathBuf::from(strsub::replace_thru(format!("{}-{}.jar", n[1], n[2]), Self::lib_replace))),
                4 => Some(PathBuf::from(strsub::replace_thru(format!("{}-{}-{}.jar", n[1], n[2], n[3]), Self::lib_replace))),
                _ => None
            }
        }
    }

    fn get_artifact_path(name: &str, classifier: Option<&str>) -> Option<PathBuf> {
        let Some(mut p) = Self::get_artifact_base_dir(name) else {
            return None;
        };

        p.push(Self::get_artifact_filename(name, classifier)?);
        Some(p)
    }
    
    fn create_download(&self, lib: &Library, os: OperatingSystem) -> Option<VerifiedDownload> {
        let classifier = lib.natives.as_ref()?.get(&os).map(|s| s.as_str());

        if lib.url.is_some() || lib.downloads.is_none() {
            // TODO: derive download URL in this situation?
            warn!("BUG: Deprecated case for library {}: url present or downloads missing. The launcher does not support out-of-line checksums at this time. Not downloading this library.", lib.name);
            return None;
        }

        let dlinfo = lib.downloads.as_ref()?.get_download_info(classifier)?;
        // drinking game: take a shot once per heap allocation
        let path = self.home.join(dlinfo.path.as_ref().map(PathBuf::from).or_else(|| Self::get_artifact_path(lib.name.as_str(), classifier))?);

        Some(VerifiedDownload::new(dlinfo.url.as_ref()?, path.as_path(), dlinfo.size, dlinfo.sha1))
    }
}

impl SystemInfo {
    fn new() -> SystemInfo {
        let os = match OS {
            "windows" => OperatingSystem::Windows,
            "macos" => OperatingSystem::MacOS,
            "linux" => OperatingSystem::Linux,
            _ => OperatingSystem::Unknown // could probably consider "hurd" and "*bsd" to be linux...
        };

        let mut os_version = System::os_version().unwrap_or_default();
        if os == OperatingSystem::Windows && (os_version.starts_with("10") || os_version.starts_with("11")) {
            os_version.replace_range(..2, "10.0"); // minecraft expects this funny business...
        }

        let mut arch = ARCH.to_owned();
        if arch == "x86_64" {
            // this nomenclature is preferred, since some versions expect the arch containing "x86" to mean 32-bit.
            arch.replace_range(.., "amd64");
        }

        SystemInfo {
            os,
            os_version,
            arch
        }
    }

    fn is_our_os(&self, os: OperatingSystem) -> bool {
        if self.os == OperatingSystem::Unknown {
            return false;
        }

        self.os == os
    }

    fn applies(&self, restriction: &OSRestriction) -> bool {
        restriction.os.is_none_or(|os| self.is_our_os(os))
            && restriction.version.as_deref().is_none_or(|pat| pat.is_match(&self.os_version))
            && restriction.arch.as_deref().is_none_or(|pat| pat.is_match(&self.arch))
    }
}