use futures_util::StreamExt;
use serde::Serialize;
use std::io::Write;
use tauri::{AppHandle, Emitter};

use crate::sidecar::{SidecarManager, DATA_DIR};

const REPO_API: &str = "https://repo.anhonesthost.net/api/v1/repos/MacroPad/voice-to-notes";

#[derive(Serialize, Clone)]
struct DownloadProgress {
    downloaded: u64,
    total: u64,
    percent: u8,
}

#[derive(Serialize)]
pub struct UpdateInfo {
    pub current_version: String,
    pub latest_version: String,
}

/// Read the locally installed sidecar version from `sidecar-version.txt`.
/// Returns `None` if the file doesn't exist or can't be read.
fn read_local_sidecar_version() -> Option<String> {
    let data_dir = DATA_DIR.get()?;
    let version_file = data_dir.join("sidecar-version.txt");
    std::fs::read_to_string(version_file)
        .ok()
        .map(|v| v.trim().to_string())
        .filter(|v| !v.is_empty())
}

/// Write the sidecar version to `sidecar-version.txt` after a successful download.
fn write_local_sidecar_version(version: &str) -> Result<(), String> {
    let data_dir = DATA_DIR.get().ok_or("App data directory not initialized")?;
    let version_file = data_dir.join("sidecar-version.txt");
    std::fs::write(&version_file, version)
        .map_err(|e| format!("Failed to write sidecar version file: {}", e))
}

/// Fetch releases from the Gitea API and find the latest sidecar release
/// (one whose tag_name starts with "sidecar-v").
async fn fetch_latest_sidecar_release(
    client: &reqwest::Client,
) -> Result<serde_json::Value, String> {
    let releases_url = format!("{}/releases?limit=20", REPO_API);
    let resp = client
        .get(&releases_url)
        .header("Accept", "application/json")
        .send()
        .await
        .map_err(|e| format!("Failed to fetch releases: {}", e))?;

    if !resp.status().is_success() {
        return Err(format!("Failed to fetch releases: HTTP {}", resp.status()));
    }

    let releases = resp
        .json::<Vec<serde_json::Value>>()
        .await
        .map_err(|e| format!("Failed to parse releases JSON: {}", e))?;

    releases
        .into_iter()
        .find(|r| {
            r["tag_name"]
                .as_str()
                .map_or(false, |t| t.starts_with("sidecar-v"))
        })
        .ok_or_else(|| "No sidecar release found".to_string())
}

/// Extract the version string from a sidecar tag name (e.g. "sidecar-v1.0.1" -> "1.0.1").
fn version_from_sidecar_tag(tag: &str) -> &str {
    tag.strip_prefix("sidecar-v").unwrap_or(tag)
}

/// Check if the sidecar binary exists for the currently installed version.
#[tauri::command]
pub fn check_sidecar() -> bool {
    let data_dir = match DATA_DIR.get() {
        Some(d) => d,
        None => return false,
    };

    let version = match read_local_sidecar_version() {
        Some(v) => v,
        None => return false,
    };

    let binary_name = if cfg!(target_os = "windows") {
        "voice-to-notes-sidecar.exe"
    } else {
        "voice-to-notes-sidecar"
    };

    let extract_dir = data_dir.join(format!("sidecar-{}", version));
    extract_dir.join(binary_name).exists()
}

/// Determine the current platform name for asset downloads.
fn platform_os() -> &'static str {
    if cfg!(target_os = "windows") {
        "windows"
    } else if cfg!(target_os = "macos") {
        "macos"
    } else {
        "linux"
    }
}

/// Determine the current architecture name for asset downloads.
fn platform_arch() -> &'static str {
    if cfg!(target_arch = "aarch64") {
        "aarch64"
    } else {
        "x86_64"
    }
}

/// Download the sidecar binary for the given variant (cpu or cuda).
#[tauri::command]
pub async fn download_sidecar(app: AppHandle, variant: String) -> Result<(), String> {
    let data_dir = DATA_DIR.get().ok_or("App data directory not initialized")?;

    let os = platform_os();
    let arch = platform_arch();
    let asset_name = format!("sidecar-{}-{}-{}.zip", os, arch, variant);

    // Fetch the latest sidecar release from Gitea API
    let client = reqwest::Client::new();
    let sidecar_release = fetch_latest_sidecar_release(&client).await?;

    let tag = sidecar_release["tag_name"]
        .as_str()
        .ok_or("No tag_name in sidecar release")?;
    let sidecar_version = version_from_sidecar_tag(tag).to_string();

    // Find the matching asset
    let assets = sidecar_release["assets"]
        .as_array()
        .ok_or("No assets found in sidecar release")?;

    let download_url = assets
        .iter()
        .find(|a| a["name"].as_str() == Some(&asset_name))
        .and_then(|a| a["browser_download_url"].as_str())
        .ok_or_else(|| {
            format!(
                "Asset '{}' not found in sidecar release {}",
                asset_name, tag
            )
        })?
        .to_string();

    // Stream download with progress events
    let response: reqwest::Response = client
        .get(&download_url)
        .send()
        .await
        .map_err(|e| format!("Failed to start download: {}", e))?;

    if !response.status().is_success() {
        return Err(format!("Download failed: HTTP {}", response.status()));
    }

    let total: u64 = response.content_length().unwrap_or(0);
    let mut downloaded: u64 = 0;
    let mut stream = response.bytes_stream();

    let zip_path = data_dir.join("sidecar.zip");
    let mut file = std::fs::File::create(&zip_path)
        .map_err(|e| format!("Failed to create zip file: {}", e))?;

    while let Some(chunk) = stream.next().await {
        let chunk: bytes::Bytes = chunk.map_err(|e| format!("Download stream error: {}", e))?;
        file.write_all(&chunk)
            .map_err(|e| format!("Failed to write chunk: {}", e))?;
        downloaded += chunk.len() as u64;
        let percent = if total > 0 {
            (downloaded * 100 / total) as u8
        } else {
            0
        };
        let _ = app.emit(
            "sidecar-download-progress",
            DownloadProgress {
                downloaded,
                total,
                percent,
            },
        );
    }

    // Extract the downloaded zip
    let extract_dir = data_dir.join(format!("sidecar-{}", sidecar_version));
    SidecarManager::extract_zip(&zip_path, &extract_dir)?;

    // Make the binary executable on Unix
    #[cfg(unix)]
    {
        use std::os::unix::fs::PermissionsExt;
        let binary_path = extract_dir.join("voice-to-notes-sidecar");
        if let Ok(meta) = std::fs::metadata(&binary_path) {
            let mut perms = meta.permissions();
            perms.set_mode(0o755);
            let _ = std::fs::set_permissions(&binary_path, perms);
        }
    }

    // Write the sidecar version file
    write_local_sidecar_version(&sidecar_version)?;

    // Clean up the zip file and old sidecar versions
    let _ = std::fs::remove_file(&zip_path);
    SidecarManager::cleanup_old_sidecars(data_dir, &sidecar_version);

    Ok(())
}

/// Check if a sidecar update is available.
#[tauri::command]
pub async fn check_sidecar_update() -> Result<Option<UpdateInfo>, String> {
    // If sidecar doesn't exist yet, return None (first launch handled separately)
    if !check_sidecar() {
        return Ok(None);
    }

    let current_version = match read_local_sidecar_version() {
        Some(v) => v,
        None => return Ok(None),
    };

    // Fetch latest sidecar release from Gitea API
    let client = reqwest::Client::new();
    let sidecar_release = fetch_latest_sidecar_release(&client).await?;

    let latest_tag = sidecar_release["tag_name"]
        .as_str()
        .ok_or("No tag_name in sidecar release")?;
    let latest_version = version_from_sidecar_tag(latest_tag);

    if latest_version != current_version {
        Ok(Some(UpdateInfo {
            current_version,
            latest_version: latest_version.to_string(),
        }))
    } else {
        Ok(None)
    }
}