use std::{
    collections::HashSet,
    io::ErrorKind,
    path::{Path, PathBuf},
    sync::Arc,
};

use eyre::WrapErr;

use super::{
    intent::{InstallIntent, InstallIntentState, read_intent, write_intent},
    unpack::Unpacker,
};
use crate::local_games::version_ini_is_regular_file;

const LOCAL_DIR: &str = "local";
const INSTALLING_DIR: &str = ".local.installing";
const BACKUP_DIR: &str = ".local.backup";
const OWNED_MARKER: &str = ".lanspread_owned";
const VERSION_TMP_FILE: &str = ".version.ini.tmp";
const VERSION_DISCARDED_FILE: &str = ".version.ini.discarded";

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
enum FsEntryState {
    Present,
    Missing,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
struct InstallFsState {
    local: FsEntryState,
    installing: FsEntryState,
    backup: FsEntryState,
}

pub async fn install(game_root: &Path, id: &str, unpacker: Arc<dyn Unpacker>) -> eyre::Result<()> {
    let eti_version = read_downloaded_version(game_root).await;
    write_intent(
        game_root,
        &InstallIntent::new(id, InstallIntentState::Installing, eti_version.clone()),
    )
    .await?;

    let result = install_inner(game_root, id, unpacker).await;
    match result {
        Ok(()) => {
            write_intent(game_root, &InstallIntent::none(id, eti_version)).await?;
            Ok(())
        }
        Err(err) => {
            if let Err(cleanup_err) = remove_dir_all_if_exists(&installing_dir(game_root)).await {
                log::warn!(
                    "Failed to clean install staging {}: {cleanup_err}",
                    installing_dir(game_root).display()
                );
            }
            write_intent(game_root, &InstallIntent::none(id, eti_version)).await?;
            Err(err)
        }
    }
}

pub async fn update(game_root: &Path, id: &str, unpacker: Arc<dyn Unpacker>) -> eyre::Result<()> {
    let eti_version = read_downloaded_version(game_root).await;
    write_intent(
        game_root,
        &InstallIntent::new(id, InstallIntentState::Updating, eti_version.clone()),
    )
    .await?;

    let result = update_inner(game_root, id, unpacker).await;
    match result {
        Ok(()) => {
            write_intent(game_root, &InstallIntent::none(id, eti_version)).await?;
            if let Err(err) = remove_dir_all_if_exists(&backup_dir(game_root)).await {
                log::warn!(
                    "Failed to clean install backup {}: {err}",
                    backup_dir(game_root).display()
                );
            }
            Ok(())
        }
        Err(err) => {
            let rollback = rollback_update(game_root).await;
            write_intent(game_root, &InstallIntent::none(id, eti_version)).await?;
            if let Err(rollback_err) = rollback {
                return Err(err.wrap_err(format!("rollback also failed: {rollback_err}")));
            }
            Err(err)
        }
    }
}

pub async fn uninstall(game_root: &Path, id: &str) -> eyre::Result<()> {
    let eti_version = read_downloaded_version(game_root).await;
    write_intent(
        game_root,
        &InstallIntent::new(id, InstallIntentState::Uninstalling, eti_version.clone()),
    )
    .await?;

    let result = uninstall_inner(game_root).await;
    match result {
        Ok(()) => {
            write_intent(game_root, &InstallIntent::none(id, eti_version)).await?;
            Ok(())
        }
        Err(err) => {
            let rollback = restore_backup(game_root).await;
            if let Err(rollback_err) = rollback {
                return Err(err.wrap_err(format!("rollback also failed: {rollback_err}")));
            }
            write_intent(game_root, &InstallIntent::none(id, eti_version)).await?;
            Err(err)
        }
    }
}

pub async fn recover_on_startup(game_dir: &Path, active_ids: &HashSet<String>) -> eyre::Result<()> {
    recover_download_transients(game_dir).await?;

    let mut entries = match tokio::fs::read_dir(game_dir).await {
        Ok(entries) => entries,
        Err(err) if err.kind() == ErrorKind::NotFound => return Ok(()),
        Err(err) => return Err(err.into()),
    };

    while let Some(entry) = entries.next_entry().await? {
        if !entry.file_type().await?.is_dir() {
            continue;
        }

        let Some(id) = entry.file_name().to_str().map(ToOwned::to_owned) else {
            continue;
        };
        if id == ".lanspread" {
            continue;
        }
        if active_ids.contains(&id) {
            log::debug!("Skipping recovery for active game root {id}");
            continue;
        }

        recover_game_root(&entry.path(), &id).await?;
    }

    Ok(())
}

pub async fn recover_game_root(game_root: &Path, id: &str) -> eyre::Result<()> {
    recover_download_transients(game_root).await?;

    let intent = read_intent(game_root, id).await;
    let fs = inspect_install_fs(game_root).await;
    match intent.state {
        InstallIntentState::None => recover_none_intent(game_root).await?,
        InstallIntentState::Installing => recover_installing(game_root, id, intent, fs).await?,
        InstallIntentState::Updating => recover_updating(game_root, id, intent, fs).await?,
        InstallIntentState::Uninstalling => recover_uninstalling(game_root, id, intent, fs).await?,
    }
    Ok(())
}

async fn install_inner(
    game_root: &Path,
    id: &str,
    unpacker: Arc<dyn Unpacker>,
) -> eyre::Result<()> {
    let local = local_dir(game_root);
    if path_is_dir(&local).await {
        eyre::bail!("game {id} is already installed");
    }

    let staging = installing_dir(game_root);
    prepare_owned_empty_dir(&staging).await?;
    unpack_archives(game_root, &staging, unpacker).await?;
    tokio::fs::rename(&staging, &local)
        .await
        .wrap_err_with(|| format!("failed to promote install for {id}"))?;
    Ok(())
}

async fn update_inner(game_root: &Path, id: &str, unpacker: Arc<dyn Unpacker>) -> eyre::Result<()> {
    let local = local_dir(game_root);
    let backup = backup_dir(game_root);
    let staging = installing_dir(game_root);

    if !path_is_dir(&local).await {
        eyre::bail!("game {id} is not installed");
    }
    prepare_backup_slot(&backup).await?;
    tokio::fs::rename(&local, &backup)
        .await
        .wrap_err_with(|| format!("failed to move existing install for {id} to backup"))?;
    drop_owned_marker(&backup).await?;

    prepare_owned_empty_dir(&staging).await?;
    unpack_archives(game_root, &staging, unpacker).await?;
    tokio::fs::rename(&staging, &local)
        .await
        .wrap_err_with(|| format!("failed to promote update for {id}"))?;
    Ok(())
}

async fn uninstall_inner(game_root: &Path) -> eyre::Result<()> {
    let local = local_dir(game_root);
    let backup = backup_dir(game_root);

    if !path_is_dir(&local).await {
        return Ok(());
    }

    prepare_backup_slot(&backup).await?;
    tokio::fs::rename(&local, &backup).await?;
    drop_owned_marker(&backup).await?;
    tokio::fs::remove_dir_all(&backup).await?;
    Ok(())
}

async fn unpack_archives(
    game_root: &Path,
    staging: &Path,
    unpacker: Arc<dyn Unpacker>,
) -> eyre::Result<()> {
    let archives = root_eti_archives(game_root).await?;
    if archives.is_empty() {
        eyre::bail!("no .eti archives found in {}", game_root.display());
    }

    for archive in archives {
        unpacker.unpack(&archive, staging).await?;
    }
    Ok(())
}

async fn root_eti_archives(game_root: &Path) -> eyre::Result<Vec<PathBuf>> {
    let mut entries = tokio::fs::read_dir(game_root).await?;
    let mut archives = Vec::new();
    while let Some(entry) = entries.next_entry().await? {
        if !entry.file_type().await?.is_file() {
            continue;
        }
        let path = entry.path();
        if path.extension().is_some_and(|extension| extension == "eti") {
            archives.push(path);
        }
    }
    archives.sort();
    Ok(archives)
}

async fn recover_none_intent(game_root: &Path) -> eyre::Result<()> {
    sweep_owned_orphan(&installing_dir(game_root)).await?;
    sweep_owned_orphan(&backup_dir(game_root)).await?;
    Ok(())
}

async fn recover_installing(
    game_root: &Path,
    id: &str,
    intent: InstallIntent,
    fs: InstallFsState,
) -> eyre::Result<()> {
    if let InstallFsState {
        installing: FsEntryState::Present,
        ..
    } = fs
    {
        remove_dir_all_if_exists(&installing_dir(game_root)).await?;
    }
    write_intent(game_root, &InstallIntent::none(id, intent.eti_version)).await
}

async fn recover_updating(
    game_root: &Path,
    id: &str,
    intent: InstallIntent,
    fs: InstallFsState,
) -> eyre::Result<()> {
    match fs {
        InstallFsState {
            local: FsEntryState::Missing,
            installing: FsEntryState::Present,
            backup: FsEntryState::Present,
        } => {
            remove_dir_all_if_exists(&installing_dir(game_root)).await?;
            restore_backup(game_root).await?;
        }
        InstallFsState {
            local: FsEntryState::Present,
            installing: FsEntryState::Present,
            backup: FsEntryState::Present,
        } => {
            remove_dir_all_if_exists(&installing_dir(game_root)).await?;
            remove_dir_all_if_exists(&backup_dir(game_root)).await?;
        }
        InstallFsState {
            local: FsEntryState::Present,
            installing: FsEntryState::Missing,
            backup: FsEntryState::Present,
        } => remove_dir_all_if_exists(&backup_dir(game_root)).await?,
        _ => {}
    }
    write_intent(game_root, &InstallIntent::none(id, intent.eti_version)).await
}

async fn recover_uninstalling(
    game_root: &Path,
    id: &str,
    intent: InstallIntent,
    fs: InstallFsState,
) -> eyre::Result<()> {
    match fs {
        InstallFsState {
            local: FsEntryState::Missing,
            installing: FsEntryState::Missing,
            backup: FsEntryState::Present,
        } => remove_dir_all_if_exists(&backup_dir(game_root)).await?,
        InstallFsState {
            local: FsEntryState::Present,
            installing: FsEntryState::Missing,
            backup: FsEntryState::Missing,
        } => uninstall_inner(game_root).await?,
        _ => {}
    }
    write_intent(game_root, &InstallIntent::none(id, intent.eti_version)).await
}

async fn recover_download_transients(root: &Path) -> eyre::Result<()> {
    remove_file_if_exists(&root.join(VERSION_TMP_FILE)).await?;
    remove_file_if_exists(&root.join(VERSION_DISCARDED_FILE)).await?;
    Ok(())
}

async fn inspect_install_fs(game_root: &Path) -> InstallFsState {
    InstallFsState {
        local: path_is_dir(&local_dir(game_root)).await.into(),
        installing: path_is_dir(&installing_dir(game_root)).await.into(),
        backup: path_is_dir(&backup_dir(game_root)).await.into(),
    }
}

async fn read_downloaded_version(game_root: &Path) -> Option<String> {
    if !version_ini_is_regular_file(game_root).await {
        return None;
    }
    match lanspread_db::db::read_version_from_ini(game_root) {
        Ok(version) => version,
        Err(err) => {
            log::warn!(
                "Failed to read version.ini in {}: {err}",
                game_root.display()
            );
            None
        }
    }
}

async fn prepare_owned_empty_dir(path: &Path) -> eyre::Result<()> {
    if path.exists() {
        if owned_marker(path).is_file() {
            tokio::fs::remove_dir_all(path).await?;
        } else {
            eyre::bail!("refusing to reuse markerless directory {}", path.display());
        }
    }
    tokio::fs::create_dir_all(path).await?;
    drop_owned_marker(path).await
}

async fn prepare_backup_slot(path: &Path) -> eyre::Result<()> {
    if !path.exists() {
        return Ok(());
    }
    if owned_marker(path).is_file() {
        tokio::fs::remove_dir_all(path).await?;
        return Ok(());
    }
    eyre::bail!("refusing to replace markerless backup {}", path.display());
}

async fn drop_owned_marker(path: &Path) -> eyre::Result<()> {
    tokio::fs::write(owned_marker(path), []).await?;
    Ok(())
}

async fn sweep_owned_orphan(path: &Path) -> eyre::Result<()> {
    if !path.exists() {
        return Ok(());
    }
    if owned_marker(path).is_file() {
        remove_dir_all_if_exists(path).await?;
    } else {
        log::warn!(
            "Leaving markerless reserved directory untouched: {}",
            path.display()
        );
    }
    Ok(())
}

async fn rollback_update(game_root: &Path) -> eyre::Result<()> {
    remove_dir_all_if_exists(&installing_dir(game_root)).await?;
    restore_backup(game_root).await
}

async fn restore_backup(game_root: &Path) -> eyre::Result<()> {
    let local = local_dir(game_root);
    let backup = backup_dir(game_root);
    if !path_is_dir(&backup).await {
        return Ok(());
    }
    remove_dir_all_if_exists(&local).await?;
    tokio::fs::rename(&backup, &local).await?;
    Ok(())
}

async fn remove_file_if_exists(path: &Path) -> eyre::Result<()> {
    match tokio::fs::remove_file(path).await {
        Ok(()) => Ok(()),
        Err(err) if err.kind() == ErrorKind::NotFound => Ok(()),
        Err(err) => Err(err.into()),
    }
}

async fn remove_dir_all_if_exists(path: &Path) -> eyre::Result<()> {
    match tokio::fs::remove_dir_all(path).await {
        Ok(()) => Ok(()),
        Err(err) if err.kind() == ErrorKind::NotFound => Ok(()),
        Err(err) => Err(err.into()),
    }
}

async fn path_is_dir(path: &Path) -> bool {
    tokio::fs::metadata(path)
        .await
        .is_ok_and(|metadata| metadata.is_dir())
}

fn local_dir(game_root: &Path) -> PathBuf {
    game_root.join(LOCAL_DIR)
}

fn installing_dir(game_root: &Path) -> PathBuf {
    game_root.join(INSTALLING_DIR)
}

fn backup_dir(game_root: &Path) -> PathBuf {
    game_root.join(BACKUP_DIR)
}

fn owned_marker(path: &Path) -> PathBuf {
    path.join(OWNED_MARKER)
}

impl From<bool> for FsEntryState {
    fn from(value: bool) -> Self {
        if value { Self::Present } else { Self::Missing }
    }
}

#[cfg(test)]
mod tests {
    use std::{
        collections::HashSet,
        path::{Path, PathBuf},
        sync::{Arc, Mutex},
    };

    use super::*;
    use crate::install::unpack::UnpackFuture;

    #[derive(Default)]
    struct FakeUnpacker {
        fail: bool,
        archives: Mutex<Vec<PathBuf>>,
    }

    impl FakeUnpacker {
        fn failing() -> Self {
            Self {
                fail: true,
                archives: Mutex::new(Vec::new()),
            }
        }
    }

    impl Unpacker for FakeUnpacker {
        fn unpack<'a>(&'a self, archive: &'a Path, dest: &'a Path) -> UnpackFuture<'a> {
            Box::pin(async move {
                self.archives
                    .lock()
                    .expect("archive list should not be poisoned")
                    .push(archive.to_path_buf());
                if self.fail {
                    eyre::bail!("forced unpack failure");
                }
                tokio::fs::write(dest.join("payload.txt"), b"installed").await?;
                Ok(())
            })
        }
    }

    struct TempDir(PathBuf);

    impl TempDir {
        fn new() -> Self {
            let mut path = std::env::temp_dir();
            path.push(format!(
                "lanspread-install-{}-{}",
                std::process::id(),
                std::time::SystemTime::now()
                    .duration_since(std::time::UNIX_EPOCH)
                    .unwrap_or_default()
                    .as_nanos()
            ));
            std::fs::create_dir_all(&path).expect("temp dir should be created");
            Self(path)
        }

        fn game_root(&self) -> PathBuf {
            self.0.join("game")
        }
    }

    impl Drop for TempDir {
        fn drop(&mut self) {
            let _ = std::fs::remove_dir_all(&self.0);
        }
    }

    fn write_file(path: &Path, bytes: &[u8]) {
        if let Some(parent) = path.parent() {
            std::fs::create_dir_all(parent).expect("parent dir should be created");
        }
        std::fs::write(path, bytes).expect("file should be written");
    }

    fn successful_unpacker() -> Arc<dyn Unpacker> {
        Arc::new(FakeUnpacker::default())
    }

    #[tokio::test]
    async fn install_success_promotes_staging_and_clears_intent() {
        let temp = TempDir::new();
        let root = temp.game_root();
        write_file(&root.join("game.eti"), b"archive");
        write_file(&root.join("version.ini"), b"20250101");

        install(&root, "game", successful_unpacker())
            .await
            .expect("install should succeed");

        assert!(root.join("local").join("payload.txt").is_file());
        assert!(!root.join(".local.installing").exists());
        let intent = read_intent(&root, "game").await;
        assert_eq!(intent.state, InstallIntentState::None);
    }

    #[tokio::test]
    async fn install_unpacks_multiple_root_eti_archives_in_sorted_order() {
        let temp = TempDir::new();
        let root = temp.game_root();
        write_file(&root.join("b.eti"), b"archive");
        write_file(&root.join("a.eti"), b"archive");
        write_file(&root.join("version.ini"), b"20250101");
        let unpacker = Arc::new(FakeUnpacker::default());

        install(&root, "game", unpacker.clone())
            .await
            .expect("install should succeed");

        let archives = unpacker
            .archives
            .lock()
            .expect("archive list should not be poisoned")
            .iter()
            .filter_map(|path| path.file_name()?.to_str().map(ToOwned::to_owned))
            .collect::<Vec<_>>();
        assert_eq!(archives, vec!["a.eti", "b.eti"]);
    }

    #[tokio::test]
    async fn update_failure_restores_previous_local() {
        let temp = TempDir::new();
        let root = temp.game_root();
        write_file(&root.join("game.eti"), b"archive");
        write_file(&root.join("version.ini"), b"20250101");
        write_file(&root.join("local").join("old.txt"), b"old");

        let err = update(&root, "game", Arc::new(FakeUnpacker::failing()))
            .await
            .expect_err("update should fail");

        assert!(err.to_string().contains("forced unpack failure"));
        assert!(root.join("local").join("old.txt").is_file());
        assert!(!root.join(".local.installing").exists());
        assert!(!root.join(".local.backup").exists());
        let intent = read_intent(&root, "game").await;
        assert_eq!(intent.state, InstallIntentState::None);
    }

    #[tokio::test]
    async fn update_success_promotes_new_local_and_removes_backup() {
        let temp = TempDir::new();
        let root = temp.game_root();
        write_file(&root.join("game.eti"), b"archive");
        write_file(&root.join("version.ini"), b"20250101");
        write_file(&root.join("local").join("old.txt"), b"old");

        update(&root, "game", successful_unpacker())
            .await
            .expect("update should succeed");

        assert!(root.join("local").join("payload.txt").is_file());
        assert!(!root.join("local").join("old.txt").exists());
        assert!(!root.join(".local.installing").exists());
        assert!(!root.join(".local.backup").exists());
        let intent = read_intent(&root, "game").await;
        assert_eq!(intent.state, InstallIntentState::None);
    }

    #[tokio::test]
    async fn uninstall_removes_only_local_install() {
        let temp = TempDir::new();
        let root = temp.game_root();
        write_file(&root.join("game.eti"), b"archive");
        write_file(&root.join("version.ini"), b"20250101");
        write_file(&root.join("local").join("payload.txt"), b"installed");

        uninstall(&root, "game")
            .await
            .expect("uninstall should succeed");

        assert!(!root.join("local").exists());
        assert!(root.join("game.eti").is_file());
        assert!(root.join("version.ini").is_file());
    }

    #[tokio::test]
    async fn recovery_restores_backup_for_interrupted_update() {
        let temp = TempDir::new();
        let root = temp.game_root();
        write_file(&root.join("version.ini"), b"20250101");
        write_file(&root.join(".local.backup").join("old.txt"), b"old");
        write_file(&root.join(".local.installing").join("new.txt"), b"new");
        write_file(&root.join(".local.backup").join(OWNED_MARKER), b"");
        write_file(&root.join(".local.installing").join(OWNED_MARKER), b"");
        write_intent(
            &root,
            &InstallIntent::new(
                "game",
                InstallIntentState::Updating,
                Some("20250101".into()),
            ),
        )
        .await
        .expect("intent should be written");

        recover_game_root(&root, "game")
            .await
            .expect("recovery should succeed");

        assert!(root.join("local").join("old.txt").is_file());
        assert!(!root.join(".local.installing").exists());
        assert!(!root.join(".local.backup").exists());
        assert_eq!(
            read_intent(&root, "game").await.state,
            InstallIntentState::None
        );
    }

    #[tokio::test]
    async fn none_recovery_leaves_markerless_reserved_dirs_untouched() {
        let temp = TempDir::new();
        let root = temp.game_root();
        write_file(&root.join(".local.backup").join("user.txt"), b"user");

        recover_game_root(&root, "game")
            .await
            .expect("recovery should succeed");

        assert!(root.join(".local.backup").join("user.txt").is_file());
    }

    #[tokio::test]
    async fn download_recovery_sweeps_reserved_version_files() {
        let temp = TempDir::new();
        let root = temp.game_root();
        write_file(&root.join(VERSION_TMP_FILE), b"tmp");
        write_file(&root.join(VERSION_DISCARDED_FILE), b"old");

        recover_game_root(&root, "game")
            .await
            .expect("recovery should succeed");

        assert!(!root.join(VERSION_TMP_FILE).exists());
        assert!(!root.join(VERSION_DISCARDED_FILE).exists());
    }

    #[tokio::test]
    async fn startup_recovery_skips_active_game_roots() {
        let temp = TempDir::new();
        let active_root = temp.0.join("active");
        let inactive_root = temp.0.join("inactive");
        write_file(&active_root.join(VERSION_TMP_FILE), b"tmp");
        write_file(&inactive_root.join(VERSION_TMP_FILE), b"tmp");

        recover_on_startup(&temp.0, &HashSet::from(["active".to_string()]))
            .await
            .expect("recovery should succeed");

        assert!(active_root.join(VERSION_TMP_FILE).is_file());
        assert!(!inactive_root.join(VERSION_TMP_FILE).exists());
    }
}