use std::env::consts::ARCH;
use std::ffi::OsString;
use std::{any::Any, path::PathBuf};

use anyhow::{anyhow, Context, Result};
use async_compression::futures::bufread::XzDecoder;
use async_tar::Archive;
use async_trait::async_trait;
use futures::{io::BufReader, StreamExt};
use smol::fs;

use language::{LanguageServerName, LspAdapter, LspAdapterDelegate};
use lsp::LanguageServerBinary;
use util::async_maybe;
use util::github::latest_github_release;
use util::{github::GitHubLspBinaryVersion, ResultExt};

fn server_binary_arguments() -> Vec<OsString> {
    vec!["--lsp".into()]
}

pub struct HaskellLspAdapter;

#[async_trait]
impl LspAdapter for HaskellLspAdapter {
    fn name(&self) -> LanguageServerName {
        LanguageServerName("haskell-language-server".into())
    }

    fn short_name(&self) -> &'static str {
        "hls"
    }

    async fn fetch_latest_server_version(
        &self,
        delegate: &dyn LspAdapterDelegate,
    ) -> Result<Box<dyn 'static + Send + Any>> {
        // TODO: Release version should be matched against GHC version
        let release = latest_github_release(
            "haskell/haskell-language-server",
            false,
            delegate.http_client(),
        )
        .await?;
        let asset_name = format!(
            "haskell-language-server-{}-{}-apple-darwin.tar.xz",
            release.name, ARCH
        );
        let asset = release
            .assets
            .iter()
            .find(|asset| asset.name == asset_name)
            .ok_or_else(|| anyhow!("no asset found matching {:?}", asset_name))?;
        let version = GitHubLspBinaryVersion {
            name: release.name,
            url: asset.browser_download_url.clone(),
        };
        Ok(Box::new(version) as Box<_>)
    }

    async fn fetch_server_binary(
        &self,
        version: Box<dyn 'static + Send + Any>,
        container_dir: PathBuf,
        delegate: &dyn LspAdapterDelegate,
    ) -> Result<LanguageServerBinary> {
        let version = version.downcast::<GitHubLspBinaryVersion>().unwrap();
        let destination_path =
            container_dir.join(format!("haskell-language-server-{}", version.name));
        if fs::metadata(&destination_path).await.is_err() {
            let mut response = delegate
                .http_client()
                .get(&version.url, Default::default(), true)
                .await
                .context("error downloading release")?;
            let decompressed_bytes = XzDecoder::new(BufReader::new(response.body_mut()));
            let archive = Archive::new(decompressed_bytes);
            archive.unpack(&container_dir).await?;
        }
        let binary_path = destination_path.join("bin/haskell-language-server-wrapper");
        fs::set_permissions(
            &binary_path,
            <fs::Permissions as fs::unix::PermissionsExt>::from_mode(0o755),
        )
        .await?;
        Ok(LanguageServerBinary {
            path: binary_path,
            arguments: server_binary_arguments(),
        })
    }

    async fn cached_server_binary(
        &self,
        container_dir: PathBuf,
        _: &dyn LspAdapterDelegate,
    ) -> Option<LanguageServerBinary> {
        get_cached_server_binary(container_dir).await
    }

    async fn installation_test_binary(
        &self,
        container_dir: PathBuf,
    ) -> Option<LanguageServerBinary> {
        get_cached_server_binary(container_dir)
            .await
            .map(|mut binary| {
                binary.arguments = vec!["--help".into()];
                binary
            })
    }
}

async fn get_cached_server_binary(container_dir: PathBuf) -> Option<LanguageServerBinary> {
    async_maybe!({
        let mut last_binary_path = None;
        let mut entries = fs::read_dir(&container_dir).await?;
        while let Some(entry) = entries.next().await {
            let entry = entry?;
            if entry.file_type().await?.is_file()
                && entry
                    .file_name()
                    .to_str()
                    .map_or(false, |name| name == "haskell-language-server-wrapper")
            {
                last_binary_path = Some(entry.path());
            }
        }

        if let Some(path) = last_binary_path {
            Ok(LanguageServerBinary {
                path,
                arguments: server_binary_arguments(),
            })
        } else {
            Err(anyhow!("no cached binary"))
        }
    })
    .await
    .log_err()
}