//! Update system: check for updates, download deltas, apply with rollback.

use anyhow::{Context, Result};
use serde::{Deserialize, Serialize};
use std::path::Path;
use tokio::fs;
use tracing::{debug, info};

const UPDATE_MANIFEST_URL: &str =
    "https://raw.githubusercontent.com/archipelago-os/releases/main/manifest.json";
const UPDATE_STATE_FILE: &str = "update_state.json";

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct UpdateManifest {
    pub version: String,
    pub release_date: String,
    pub changelog: Vec<String>,
    pub components: Vec<ComponentUpdate>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ComponentUpdate {
    pub name: String,
    pub current_version: String,
    pub new_version: String,
    pub download_url: String,
    pub sha256: String,
    pub size_bytes: u64,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct UpdateState {
    pub current_version: String,
    pub last_check: Option<String>,
    pub available_update: Option<UpdateManifest>,
    pub update_in_progress: bool,
    pub rollback_available: bool,
}

impl Default for UpdateState {
    fn default() -> Self {
        Self {
            current_version: env!("CARGO_PKG_VERSION").to_string(),
            last_check: None,
            available_update: None,
            update_in_progress: false,
            rollback_available: false,
        }
    }
}

pub async fn load_state(data_dir: &Path) -> Result<UpdateState> {
    let path = data_dir.join(UPDATE_STATE_FILE);
    if !path.exists() {
        let state = UpdateState::default();
        save_state(data_dir, &state).await?;
        return Ok(state);
    }
    let data = fs::read_to_string(&path)
        .await
        .context("Reading update state")?;
    serde_json::from_str(&data).context("Parsing update state")
}

pub async fn save_state(data_dir: &Path, state: &UpdateState) -> Result<()> {
    let path = data_dir.join(UPDATE_STATE_FILE);
    let data = serde_json::to_string_pretty(state)?;
    fs::write(&path, data)
        .await
        .context("Writing update state")
}

/// Check for available updates by fetching the release manifest.
pub async fn check_for_updates(data_dir: &Path) -> Result<UpdateState> {
    let mut state = load_state(data_dir).await?;

    info!("Checking for updates...");
    let client = reqwest::Client::builder()
        .timeout(std::time::Duration::from_secs(15))
        .build()
        .context("Failed to create HTTP client")?;

    match client.get(UPDATE_MANIFEST_URL).send().await {
        Ok(resp) if resp.status().is_success() => {
            let manifest: UpdateManifest = resp
                .json()
                .await
                .context("Failed to parse update manifest")?;

            if manifest.version != state.current_version {
                info!(
                    current = %state.current_version,
                    available = %manifest.version,
                    "Update available"
                );
                state.available_update = Some(manifest);
            } else {
                debug!("Already on latest version: {}", state.current_version);
                state.available_update = None;
            }
        }
        Ok(resp) => {
            debug!("Update check returned status: {}", resp.status());
        }
        Err(e) => {
            debug!("Update check failed (offline?): {}", e);
        }
    }

    state.last_check = Some(chrono::Utc::now().to_rfc3339());
    save_state(data_dir, &state).await?;
    Ok(state)
}

/// Get current update status without checking remote.
pub async fn get_status(data_dir: &Path) -> Result<UpdateState> {
    load_state(data_dir).await
}

/// Dismiss the available update notification.
pub async fn dismiss_update(data_dir: &Path) -> Result<()> {
    let mut state = load_state(data_dir).await?;
    state.available_update = None;
    save_state(data_dir, &state).await
}