//! OAuth PKCE flow — browser-based login for API providers.

use tracing::{info, warn};

/// Run a browser-based OAuth PKCE flow for the given provider.
///
/// Flow: look up config by provider name ("zen"/"opencode", "openai",
/// or a custom provider via env vars) → bind a loopback server → generate
/// a PKCE code verifier and challenge → build the authorisation URL →
/// wait for the redirect code on the loopback server (with a 120s timeout)
/// → exchange the code for a token → save the token to
/// `~/.config/zesdex/oauth_{provider}.json`.
///
/// Why: the `webbrowser::open` call is currently commented out; the user
/// must open the auth URL manually until that line is reinstated.
///
/// Return: a success message on completion, or an error if the flow fails
/// at any step.
pub(super) fn run_oauth_flow(provider: &str) -> anyhow::Result<String> {
    info!(provider = provider, "starting OAuth flow");
    use zesdex_iam::domain::oauth::OAuthConfig;
    use zesdex_iam::domain::service::OAuthService;
    use zesdex_iam::application::oauth_service::OAuthServiceImpl;
    use zesdex_iam::infrastructure::persistence::oauth_repo::FileSystemOAuthRepository;
    use zesdex_iam::infrastructure::oauth_loopback::LoopbackServer;

    let config = match provider {
        "zen" | "opencode" => OAuthConfig {
            auth_url: "https://opencode.ai/zen/oauth/authorize".to_string(),
            token_url: "https://opencode.ai/zen/oauth/token".to_string(),
            client_id: std::env::var("ZEN_CLIENT_ID")
                .unwrap_or_else(|_| "zesdex".to_string()),
            client_secret: std::env::var("ZEN_CLIENT_SECRET").ok(),
            scopes: vec![
                "openid".to_string(),
                "profile".to_string(),
                "email".to_string(),
            ],
        },
        "openai" => OAuthConfig {
            auth_url: "https://auth0.openai.com/authorize".to_string(),
            token_url: "https://auth0.openai.com/oauth/token".to_string(),
            client_id: std::env::var("OPENAI_CLIENT_ID")
                .unwrap_or_else(|_| "zesdex".to_string()),
            client_secret: std::env::var("OPENAI_CLIENT_SECRET").ok(),
            scopes: vec![
                "openid".to_string(),
                "profile".to_string(),
                "email".to_string(),
            ],
        },
        other => {
            let auth_url = std::env::var(format!("{}_AUTH_URL", other.to_uppercase()))
                .map_err(|_| {
                    anyhow::anyhow!(
                        "unknown provider '{}'. Set {}_AUTH_URL env var.",
                        other,
                        other.to_uppercase()
                    )
                })?;
            let token_url = std::env::var(format!("{}_TOKEN_URL", other.to_uppercase()))
                .map_err(|_| anyhow::anyhow!("{}_TOKEN_URL not set", other.to_uppercase()))?;
            let client_id = std::env::var(format!("{}_CLIENT_ID", other.to_uppercase()))
                .unwrap_or_else(|_| "zesdex".to_string());
            OAuthConfig {
                auth_url,
                token_url,
                client_id,
                client_secret: std::env::var(format!("{}_CLIENT_SECRET", other.to_uppercase()))
                    .ok(),
                scopes: vec![
                    "openid".to_string(),
                    "profile".to_string(),
                    "email".to_string(),
                ],
            }
        }
    };

    let server = LoopbackServer::bind()?;
    let redirect_uri = server.redirect_uri();

    let token_path = dirs::config_dir()
        .unwrap_or_else(|| std::path::PathBuf::from("."))
        .join("zesdex")
        .join(format!("oauth_{provider}.json"));

    let oauth_service = OAuthServiceImpl::new(FileSystemOAuthRepository::new(), token_path);

    let (auth_url, state) = oauth_service.start_flow(&config, &redirect_uri)?;
    if auth_url.is_empty() {
        warn!("OAuth auth_url was empty for provider '{}'", provider);
    } else if webbrowser::open(&auth_url).is_err() {
        warn!(
            "OAuth could not open browser for '{}'; user must open URL manually:\n{}",
            provider,
            auth_url
        );
    }

    info!(provider = provider, "waiting for OAuth redirect");
    let code = server.wait_for_code(120_000, &state)?;

    oauth_service
        .complete_flow(&config, &redirect_uri, &code, &state)
        .map_err(|e| anyhow::anyhow!("{e}"))?;

    info!(provider = provider, "OAuth flow completed");
    Ok(format!("Successfully authenticated with {provider}."))
}