//! Axum-based HTTP gateway with proper HTTP/1.1 compliance, body limits, and timeouts.
//!
//! This module replaces the raw TCP implementation with axum for:
//! - Proper HTTP/1.1 parsing and compliance
//! - Content-Length validation (handled by hyper)
//! - Request body size limits (64KB max)
//! - Request timeouts (30s) to prevent slow-loris attacks
//! - Header sanitization (handled by axum/hyper)

use crate::channels::{Channel, WhatsAppChannel};
use crate::config::Config;
use crate::memory::{self, Memory, MemoryCategory};
use crate::providers::{self, Provider};
use crate::security::pairing::{constant_time_eq, is_public_bind, PairingGuard};
use anyhow::Result;
use axum::{
    body::Bytes,
    extract::{Query, State},
    http::{header, HeaderMap, StatusCode},
    response::{IntoResponse, Json},
    routing::{get, post},
    Router,
};
use std::net::SocketAddr;
use std::sync::Arc;
use tower_http::limit::RequestBodyLimitLayer;

/// Maximum request body size (64KB) — prevents memory exhaustion
pub const MAX_BODY_SIZE: usize = 65_536;
/// Request timeout (30s) — prevents slow-loris attacks
pub const REQUEST_TIMEOUT_SECS: u64 = 30;

/// Shared state for all axum handlers
#[derive(Clone)]
pub struct AppState {
    pub provider: Arc<dyn Provider>,
    pub model: String,
    pub temperature: f64,
    pub mem: Arc<dyn Memory>,
    pub auto_save: bool,
    pub webhook_secret: Option<Arc<str>>,
    pub pairing: Arc<PairingGuard>,
    pub whatsapp: Option<Arc<WhatsAppChannel>>,
}

/// Run the HTTP gateway using axum with proper HTTP/1.1 compliance.
#[allow(clippy::too_many_lines)]
pub async fn run_gateway(host: &str, port: u16, config: Config) -> Result<()> {
    // ── Security: refuse public bind without tunnel or explicit opt-in ──
    if is_public_bind(host) && config.tunnel.provider == "none" && !config.gateway.allow_public_bind
    {
        anyhow::bail!(
            "🛑 Refusing to bind to {host} — gateway would be exposed to the internet.\n\
             Fix: use --host 127.0.0.1 (default), configure a tunnel, or set\n\
             [gateway] allow_public_bind = true in config.toml (NOT recommended)."
        );
    }

    let addr: SocketAddr = format!("{host}:{port}").parse()?;
    let listener = tokio::net::TcpListener::bind(addr).await?;
    let actual_port = listener.local_addr()?.port();
    let display_addr = format!("{host}:{actual_port}");

    let provider: Arc<dyn Provider> = Arc::from(providers::create_resilient_provider(
        config.default_provider.as_deref().unwrap_or("openrouter"),
        config.api_key.as_deref(),
        &config.reliability,
    )?);
    let model = config
        .default_model
        .clone()
        .unwrap_or_else(|| "anthropic/claude-sonnet-4-20250514".into());
    let temperature = config.default_temperature;
    let mem: Arc<dyn Memory> = Arc::from(memory::create_memory(
        &config.memory,
        &config.workspace_dir,
        config.api_key.as_deref(),
    )?);

    // Extract webhook secret for authentication
    let webhook_secret: Option<Arc<str>> = config
        .channels_config
        .webhook
        .as_ref()
        .and_then(|w| w.secret.as_deref())
        .map(Arc::from);

    // WhatsApp channel (if configured)
    let whatsapp_channel: Option<Arc<WhatsAppChannel>> =
        config.channels_config.whatsapp.as_ref().map(|wa| {
            Arc::new(WhatsAppChannel::new(
                wa.access_token.clone(),
                wa.phone_number_id.clone(),
                wa.verify_token.clone(),
                wa.allowed_numbers.clone(),
            ))
        });

    // ── Pairing guard ──────────────────────────────────────
    let pairing = Arc::new(PairingGuard::new(
        config.gateway.require_pairing,
        &config.gateway.paired_tokens,
    ));

    // ── Tunnel ────────────────────────────────────────────────
    let tunnel = crate::tunnel::create_tunnel(&config.tunnel)?;
    let mut tunnel_url: Option<String> = None;

    if let Some(ref tun) = tunnel {
        println!("🔗 Starting {} tunnel...", tun.name());
        match tun.start(host, actual_port).await {
            Ok(url) => {
                println!("🌐 Tunnel active: {url}");
                tunnel_url = Some(url);
            }
            Err(e) => {
                println!("⚠️  Tunnel failed to start: {e}");
                println!("   Falling back to local-only mode.");
            }
        }
    }

    println!("🦀 ZeroClaw Gateway listening on http://{display_addr}");
    if let Some(ref url) = tunnel_url {
        println!("  🌐 Public URL: {url}");
    }
    println!("  POST /pair      — pair a new client (X-Pairing-Code header)");
    println!("  POST /webhook   — {{\"message\": \"your prompt\"}}");
    if whatsapp_channel.is_some() {
        println!("  GET  /whatsapp  — Meta webhook verification");
        println!("  POST /whatsapp  — WhatsApp message webhook");
    }
    println!("  GET  /health    — health check");
    if let Some(code) = pairing.pairing_code() {
        println!();
        println!("  🔐 PAIRING REQUIRED — use this one-time code:");
        println!("     ┌──────────────┐");
        println!("     │  {code}  │");
        println!("     └──────────────┘");
        println!("     Send: POST /pair with header X-Pairing-Code: {code}");
    } else if pairing.require_pairing() {
        println!("  🔒 Pairing: ACTIVE (bearer token required)");
    } else {
        println!("  ⚠️  Pairing: DISABLED (all requests accepted)");
    }
    if webhook_secret.is_some() {
        println!("  🔒 Webhook secret: ENABLED");
    }
    println!("  Press Ctrl+C to stop.\n");

    crate::health::mark_component_ok("gateway");

    // Build shared state
    let state = AppState {
        provider,
        model,
        temperature,
        mem,
        auto_save: config.memory.auto_save,
        webhook_secret,
        pairing,
        whatsapp: whatsapp_channel,
    };

    // Build router with middleware
    // Note: Body limit layer prevents memory exhaustion from oversized requests
    // Timeout is handled by tokio's TcpListener accept timeout and hyper's built-in timeouts
    let app = Router::new()
        .route("/health", get(handle_health))
        .route("/pair", post(handle_pair))
        .route("/webhook", post(handle_webhook))
        .route("/whatsapp", get(handle_whatsapp_verify))
        .route("/whatsapp", post(handle_whatsapp_message))
        .with_state(state)
        .layer(RequestBodyLimitLayer::new(MAX_BODY_SIZE));

    // Run the server
    axum::serve(listener, app).await?;

    Ok(())
}

// ══════════════════════════════════════════════════════════════════════════════
// AXUM HANDLERS
// ══════════════════════════════════════════════════════════════════════════════

/// GET /health — always public (no secrets leaked)
async fn handle_health(State(state): State<AppState>) -> impl IntoResponse {
    let body = serde_json::json!({
        "status": "ok",
        "paired": state.pairing.is_paired(),
        "runtime": crate::health::snapshot_json(),
    });
    Json(body)
}

/// POST /pair — exchange one-time code for bearer token
async fn handle_pair(State(state): State<AppState>, headers: HeaderMap) -> impl IntoResponse {
    let code = headers
        .get("X-Pairing-Code")
        .and_then(|v| v.to_str().ok())
        .unwrap_or("");

    match state.pairing.try_pair(code) {
        Ok(Some(token)) => {
            tracing::info!("🔐 New client paired successfully");
            let body = serde_json::json!({
                "paired": true,
                "token": token,
                "message": "Save this token — use it as Authorization: Bearer <token>"
            });
            (StatusCode::OK, Json(body))
        }
        Ok(None) => {
            tracing::warn!("🔐 Pairing attempt with invalid code");
            let err = serde_json::json!({"error": "Invalid pairing code"});
            (StatusCode::FORBIDDEN, Json(err))
        }
        Err(lockout_secs) => {
            tracing::warn!(
                "🔐 Pairing locked out — too many failed attempts ({lockout_secs}s remaining)"
            );
            let err = serde_json::json!({
                "error": format!("Too many failed attempts. Try again in {lockout_secs}s."),
                "retry_after": lockout_secs
            });
            (StatusCode::TOO_MANY_REQUESTS, Json(err))
        }
    }
}

/// Webhook request body
#[derive(serde::Deserialize)]
pub struct WebhookBody {
    pub message: String,
}

/// POST /webhook — main webhook endpoint
async fn handle_webhook(
    State(state): State<AppState>,
    headers: HeaderMap,
    body: Result<Json<WebhookBody>, axum::extract::rejection::JsonRejection>,
) -> impl IntoResponse {
    // ── Bearer token auth (pairing) ──
    if state.pairing.require_pairing() {
        let auth = headers
            .get(header::AUTHORIZATION)
            .and_then(|v| v.to_str().ok())
            .unwrap_or("");
        let token = auth.strip_prefix("Bearer ").unwrap_or("");
        if !state.pairing.is_authenticated(token) {
            tracing::warn!("Webhook: rejected — not paired / invalid bearer token");
            let err = serde_json::json!({
                "error": "Unauthorized — pair first via POST /pair, then send Authorization: Bearer <token>"
            });
            return (StatusCode::UNAUTHORIZED, Json(err));
        }
    }

    // ── Webhook secret auth (optional, additional layer) ──
    if let Some(ref secret) = state.webhook_secret {
        let header_val = headers
            .get("X-Webhook-Secret")
            .and_then(|v| v.to_str().ok());
        match header_val {
            Some(val) if constant_time_eq(val, secret.as_ref()) => {}
            _ => {
                tracing::warn!("Webhook: rejected request — invalid or missing X-Webhook-Secret");
                let err = serde_json::json!({"error": "Unauthorized — invalid or missing X-Webhook-Secret header"});
                return (StatusCode::UNAUTHORIZED, Json(err));
            }
        }
    }

    // ── Parse body ──
    let Json(webhook_body) = match body {
        Ok(b) => b,
        Err(e) => {
            let err = serde_json::json!({
                "error": format!("Invalid JSON: {e}. Expected: {{\"message\": \"...\"}}")
            });
            return (StatusCode::BAD_REQUEST, Json(err));
        }
    };

    let message = &webhook_body.message;

    if state.auto_save {
        let _ = state
            .mem
            .store("webhook_msg", message, MemoryCategory::Conversation)
            .await;
    }

    match state
        .provider
        .chat(message, &state.model, state.temperature)
        .await
    {
        Ok(response) => {
            let body = serde_json::json!({"response": response, "model": state.model});
            (StatusCode::OK, Json(body))
        }
        Err(e) => {
            tracing::error!("LLM error: {e:#}");
            let err = serde_json::json!({"error": "Internal error processing your request"});
            (StatusCode::INTERNAL_SERVER_ERROR, Json(err))
        }
    }
}

/// `WhatsApp` verification query params
#[derive(serde::Deserialize)]
pub struct WhatsAppVerifyQuery {
    #[serde(rename = "hub.mode")]
    pub mode: Option<String>,
    #[serde(rename = "hub.verify_token")]
    pub verify_token: Option<String>,
    #[serde(rename = "hub.challenge")]
    pub challenge: Option<String>,
}

/// GET /whatsapp — Meta webhook verification
async fn handle_whatsapp_verify(
    State(state): State<AppState>,
    Query(params): Query<WhatsAppVerifyQuery>,
) -> impl IntoResponse {
    let Some(ref wa) = state.whatsapp else {
        return (StatusCode::NOT_FOUND, "WhatsApp not configured".to_string());
    };

    // Verify the token matches
    if params.mode.as_deref() == Some("subscribe")
        && params.verify_token.as_deref() == Some(wa.verify_token())
    {
        if let Some(ch) = params.challenge {
            tracing::info!("WhatsApp webhook verified successfully");
            return (StatusCode::OK, ch);
        }
        return (StatusCode::BAD_REQUEST, "Missing hub.challenge".to_string());
    }

    tracing::warn!("WhatsApp webhook verification failed — token mismatch");
    (StatusCode::FORBIDDEN, "Forbidden".to_string())
}

/// POST /whatsapp — incoming message webhook
async fn handle_whatsapp_message(State(state): State<AppState>, body: Bytes) -> impl IntoResponse {
    let Some(ref wa) = state.whatsapp else {
        return (
            StatusCode::NOT_FOUND,
            Json(serde_json::json!({"error": "WhatsApp not configured"})),
        );
    };

    // Parse JSON body
    let Ok(payload) = serde_json::from_slice::<serde_json::Value>(&body) else {
        return (
            StatusCode::BAD_REQUEST,
            Json(serde_json::json!({"error": "Invalid JSON payload"})),
        );
    };

    // Parse messages from the webhook payload
    let messages = wa.parse_webhook_payload(&payload);

    if messages.is_empty() {
        // Acknowledge the webhook even if no messages (could be status updates)
        return (StatusCode::OK, Json(serde_json::json!({"status": "ok"})));
    }

    // Process each message
    for msg in &messages {
        tracing::info!(
            "WhatsApp message from {}: {}",
            msg.sender,
            if msg.content.len() > 50 {
                format!("{}...", &msg.content[..50])
            } else {
                msg.content.clone()
            }
        );

        // Auto-save to memory
        if state.auto_save {
            let _ = state
                .mem
                .store(
                    &format!("whatsapp_{}", msg.sender),
                    &msg.content,
                    MemoryCategory::Conversation,
                )
                .await;
        }

        // Call the LLM
        match state
            .provider
            .chat(&msg.content, &state.model, state.temperature)
            .await
        {
            Ok(response) => {
                // Send reply via WhatsApp
                if let Err(e) = wa.send(&response, &msg.sender).await {
                    tracing::error!("Failed to send WhatsApp reply: {e}");
                }
            }
            Err(e) => {
                tracing::error!("LLM error for WhatsApp message: {e:#}");
                let _ = wa
                    .send("Sorry, I couldn't process your message right now.", &msg.sender)
                    .await;
            }
        }
    }

    // Acknowledge the webhook
    (StatusCode::OK, Json(serde_json::json!({"status": "ok"})))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn security_body_limit_is_64kb() {
        assert_eq!(MAX_BODY_SIZE, 65_536);
    }

    #[test]
    fn security_timeout_is_30_seconds() {
        assert_eq!(REQUEST_TIMEOUT_SECS, 30);
    }

    #[test]
    fn webhook_body_requires_message_field() {
        let valid = r#"{"message": "hello"}"#;
        let parsed: Result<WebhookBody, _> = serde_json::from_str(valid);
        assert!(parsed.is_ok());
        assert_eq!(parsed.unwrap().message, "hello");

        let missing = r#"{"other": "field"}"#;
        let parsed: Result<WebhookBody, _> = serde_json::from_str(missing);
        assert!(parsed.is_err());
    }

    #[test]
    fn whatsapp_query_fields_are_optional() {
        let q = WhatsAppVerifyQuery {
            mode: None,
            verify_token: None,
            challenge: None,
        };
        assert!(q.mode.is_none());
    }

    #[test]
    fn app_state_is_clone() {
        fn assert_clone<T: Clone>() {}
        assert_clone::<AppState>();
    }
}