//! WhatsApp Business API integration.
//!
//! Provides:
//! - [`WhatsAppTransport`] — a [`ChatTransport`] that sends messages via the
//!   Meta Graph API (`graph.facebook.com/v21.0/{phone_number_id}/messages`).
//! - [`webhook_verify`] / [`webhook_receive`] — Poem handlers for the WhatsApp
//!   webhook (GET verification handshake + POST incoming messages).

use async_trait::async_trait;
use serde::{Deserialize, Serialize};
use std::sync::Arc;

use crate::agents::AgentPool;
use crate::slog;
use crate::transport::{ChatTransport, MessageId};

// ── Graph API base URL (overridable for tests) ──────────────────────────

const GRAPH_API_BASE: &str = "https://graph.facebook.com/v21.0";

// ── WhatsApp Transport ──────────────────────────────────────────────────

/// Real WhatsApp Business API transport.
///
/// Sends text messages via `POST {GRAPH_API_BASE}/{phone_number_id}/messages`.
pub struct WhatsAppTransport {
    phone_number_id: String,
    access_token: String,
    client: reqwest::Client,
    /// Optional base URL override for tests.
    api_base: String,
}

impl WhatsAppTransport {
    pub fn new(phone_number_id: String, access_token: String) -> Self {
        Self {
            phone_number_id,
            access_token,
            client: reqwest::Client::new(),
            api_base: GRAPH_API_BASE.to_string(),
        }
    }

    #[cfg(test)]
    fn with_api_base(phone_number_id: String, access_token: String, api_base: String) -> Self {
        Self {
            phone_number_id,
            access_token,
            client: reqwest::Client::new(),
            api_base,
        }
    }

    /// Send a text message to a WhatsApp user via the Graph API.
    async fn send_text(&self, to: &str, body: &str) -> Result<String, String> {
        let url = format!(
            "{}/{}/messages",
            self.api_base, self.phone_number_id
        );

        let payload = GraphSendMessage {
            messaging_product: "whatsapp",
            to,
            r#type: "text",
            text: GraphTextBody { body },
        };

        let resp = self
            .client
            .post(&url)
            .bearer_auth(&self.access_token)
            .json(&payload)
            .send()
            .await
            .map_err(|e| format!("WhatsApp API request failed: {e}"))?;

        let status = resp.status();
        let resp_text = resp
            .text()
            .await
            .unwrap_or_else(|_| "<no body>".to_string());

        if !status.is_success() {
            return Err(format!(
                "WhatsApp API returned {status}: {resp_text}"
            ));
        }

        // Extract the message ID from the response.
        let parsed: GraphSendResponse = serde_json::from_str(&resp_text).map_err(|e| {
            format!("Failed to parse WhatsApp API response: {e} — body: {resp_text}")
        })?;

        let msg_id = parsed
            .messages
            .first()
            .map(|m| m.id.clone())
            .unwrap_or_default();

        Ok(msg_id)
    }
}

#[async_trait]
impl ChatTransport for WhatsAppTransport {
    async fn send_message(
        &self,
        recipient: &str,
        plain: &str,
        _html: &str,
    ) -> Result<MessageId, String> {
        slog!("[whatsapp] send_message to {recipient}: {plain:.80}");
        self.send_text(recipient, plain).await
    }

    async fn edit_message(
        &self,
        recipient: &str,
        _original_message_id: &str,
        plain: &str,
        html: &str,
    ) -> Result<(), String> {
        // WhatsApp does not support message editing — send a new message.
        slog!("[whatsapp] edit_message — WhatsApp does not support edits, sending new message");
        self.send_message(recipient, plain, html).await.map(|_| ())
    }

    async fn send_typing(&self, _recipient: &str, _typing: bool) -> Result<(), String> {
        // WhatsApp Business API does not expose typing indicators.
        Ok(())
    }
}

// ── Graph API request/response types ────────────────────────────────────

#[derive(Serialize)]
struct GraphSendMessage<'a> {
    messaging_product: &'a str,
    to: &'a str,
    r#type: &'a str,
    text: GraphTextBody<'a>,
}

#[derive(Serialize)]
struct GraphTextBody<'a> {
    body: &'a str,
}

#[derive(Deserialize)]
struct GraphSendResponse {
    #[serde(default)]
    messages: Vec<GraphMessageId>,
}

#[derive(Deserialize)]
struct GraphMessageId {
    id: String,
}

// ── Webhook types (Meta → us) ───────────────────────────────────────────

/// Top-level webhook payload from Meta.
#[derive(Deserialize, Debug)]
pub struct WebhookPayload {
    #[serde(default)]
    pub entry: Vec<WebhookEntry>,
}

#[derive(Deserialize, Debug)]
pub struct WebhookEntry {
    #[serde(default)]
    pub changes: Vec<WebhookChange>,
}

#[derive(Deserialize, Debug)]
pub struct WebhookChange {
    pub value: Option<WebhookValue>,
}

#[derive(Deserialize, Debug)]
pub struct WebhookValue {
    #[serde(default)]
    pub messages: Vec<WebhookMessage>,
    pub metadata: Option<WebhookMetadata>,
}

#[derive(Deserialize, Debug)]
pub struct WebhookMetadata {
    pub phone_number_id: Option<String>,
}

#[derive(Deserialize, Debug)]
pub struct WebhookMessage {
    pub from: Option<String>,
    pub r#type: Option<String>,
    pub text: Option<WebhookText>,
}

#[derive(Deserialize, Debug)]
pub struct WebhookText {
    pub body: Option<String>,
}

/// Extract text messages from a webhook payload.
///
/// Returns `(sender_phone, message_body)` pairs.
pub fn extract_text_messages(payload: &WebhookPayload) -> Vec<(String, String)> {
    let mut messages = Vec::new();
    for entry in &payload.entry {
        for change in &entry.changes {
            if let Some(value) = &change.value {
                for msg in &value.messages {
                    if msg.r#type.as_deref() == Some("text")
                        && let (Some(from), Some(text)) = (&msg.from, &msg.text)
                        && let Some(body) = &text.body
                    {
                        messages.push((from.clone(), body.clone()));
                    }
                }
            }
        }
    }
    messages
}

// ── Webhook handlers (Poem) ────────────────────────────────────────────

use poem::{Request, Response, handler, http::StatusCode, web::Query};
use std::collections::HashSet;
use std::path::PathBuf;
use std::sync::Mutex;

/// Query parameters for the webhook verification GET request.
#[derive(Deserialize)]
pub struct VerifyQuery {
    #[serde(rename = "hub.mode")]
    pub hub_mode: Option<String>,
    #[serde(rename = "hub.verify_token")]
    pub hub_verify_token: Option<String>,
    #[serde(rename = "hub.challenge")]
    pub hub_challenge: Option<String>,
}

/// Shared context for webhook handlers, injected via Poem's `Data` extractor.
pub struct WhatsAppWebhookContext {
    pub verify_token: String,
    pub transport: Arc<WhatsAppTransport>,
    pub project_root: PathBuf,
    pub agents: Arc<AgentPool>,
    pub bot_name: String,
    /// The bot's "user ID" for command dispatch (e.g. "whatsapp-bot").
    pub bot_user_id: String,
    pub ambient_rooms: Arc<Mutex<HashSet<String>>>,
}

/// GET /webhook/whatsapp — Meta verification handshake.
///
/// Meta sends `hub.mode=subscribe&hub.verify_token=<token>&hub.challenge=<challenge>`.
/// We return the challenge if the token matches.
#[handler]
pub async fn webhook_verify(
    Query(q): Query<VerifyQuery>,
    ctx: poem::web::Data<&Arc<WhatsAppWebhookContext>>,
) -> Response {
    if q.hub_mode.as_deref() == Some("subscribe")
        && q.hub_verify_token.as_deref() == Some(&ctx.verify_token)
        && let Some(challenge) = q.hub_challenge
    {
        slog!("[whatsapp] Webhook verification succeeded");
        return Response::builder()
            .status(StatusCode::OK)
            .body(challenge);
    }
    slog!("[whatsapp] Webhook verification failed");
    Response::builder()
        .status(StatusCode::FORBIDDEN)
        .body("Verification failed")
}

/// POST /webhook/whatsapp — receive incoming messages from Meta.
#[handler]
pub async fn webhook_receive(
    req: &Request,
    body: poem::Body,
    ctx: poem::web::Data<&Arc<WhatsAppWebhookContext>>,
) -> Response {
    let _ = req;
    let bytes = match body.into_bytes().await {
        Ok(b) => b,
        Err(e) => {
            slog!("[whatsapp] Failed to read webhook body: {e}");
            return Response::builder()
                .status(StatusCode::BAD_REQUEST)
                .body("Bad request");
        }
    };

    let payload: WebhookPayload = match serde_json::from_slice(&bytes) {
        Ok(p) => p,
        Err(e) => {
            slog!("[whatsapp] Failed to parse webhook payload: {e}");
            // Meta expects 200 even on parse errors to avoid retries.
            return Response::builder()
                .status(StatusCode::OK)
                .body("ok");
        }
    };

    let messages = extract_text_messages(&payload);
    if messages.is_empty() {
        // Status updates, read receipts, etc. — acknowledge silently.
        return Response::builder()
            .status(StatusCode::OK)
            .body("ok");
    }

    let ctx = Arc::clone(*ctx);
    tokio::spawn(async move {
        for (sender, text) in messages {
            slog!("[whatsapp] Message from {sender}: {text}");
            handle_incoming_message(&ctx, &sender, &text).await;
        }
    });

    Response::builder()
        .status(StatusCode::OK)
        .body("ok")
}

/// Dispatch an incoming WhatsApp message to bot commands.
async fn handle_incoming_message(
    ctx: &WhatsAppWebhookContext,
    sender: &str,
    message: &str,
) {
    use crate::matrix::commands::{CommandDispatch, try_handle_command};

    let dispatch = CommandDispatch {
        bot_name: &ctx.bot_name,
        bot_user_id: &ctx.bot_user_id,
        project_root: &ctx.project_root,
        agents: &ctx.agents,
        ambient_rooms: &ctx.ambient_rooms,
        room_id: sender,
        // WhatsApp messages are always "addressed" to the bot (1:1 or bot-specific).
        is_addressed: true,
    };

    if let Some(response) = try_handle_command(&dispatch, message) {
        slog!("[whatsapp] Sending command response to {sender}");
        if let Err(e) = ctx.transport.send_message(sender, &response, "").await {
            slog!("[whatsapp] Failed to send reply to {sender}: {e}");
        }
        return;
    }

    // Check for async commands (htop, delete).
    if let Some(htop_cmd) = crate::matrix::htop::extract_htop_command(
        message,
        &ctx.bot_name,
        &ctx.bot_user_id,
    ) {
        use crate::matrix::htop::HtopCommand;
        slog!("[whatsapp] Handling htop command from {sender}");
        match htop_cmd {
            HtopCommand::Stop => {
                // htop stop — no-op on WhatsApp since there's no persistent
                // editable message; just acknowledge.
                let _ = ctx
                    .transport
                    .send_message(sender, "htop stopped.", "")
                    .await;
            }
            HtopCommand::Start { duration_secs } => {
                // On WhatsApp, send a single snapshot instead of a live-updating
                // dashboard since we can't edit messages.
                let snapshot =
                    crate::matrix::htop::build_htop_message(&ctx.agents, 0, duration_secs);
                let _ = ctx
                    .transport
                    .send_message(sender, &snapshot, "")
                    .await;
            }
        }
        return;
    }

    if let Some(del_cmd) = crate::matrix::delete::extract_delete_command(
        message,
        &ctx.bot_name,
        &ctx.bot_user_id,
    ) {
        let response = match del_cmd {
            crate::matrix::delete::DeleteCommand::Delete { story_number } => {
                slog!("[whatsapp] Handling delete command from {sender}: story {story_number}");
                crate::matrix::delete::handle_delete(
                    &ctx.bot_name,
                    &story_number,
                    &ctx.project_root,
                    &ctx.agents,
                )
                .await
            }
            crate::matrix::delete::DeleteCommand::BadArgs => {
                format!("Usage: `{} delete <number>`", ctx.bot_name)
            }
        };
        let _ = ctx.transport.send_message(sender, &response, "").await;
        return;
    }

    // No command matched — inform the user that only commands are supported.
    // (LLM passthrough is a separate story.)
    let _ = ctx
        .transport
        .send_message(
            sender,
            "I only respond to commands right now. Try `help` to see what's available.",
            "",
        )
        .await;
}

// ── Tests ───────────────────────────────────────────────────────────────

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

    #[test]
    fn extract_text_messages_parses_valid_payload() {
        let json = r#"{
            "entry": [{
                "changes": [{
                    "value": {
                        "messages": [{
                            "from": "15551234567",
                            "type": "text",
                            "text": { "body": "help" }
                        }],
                        "metadata": { "phone_number_id": "123456" }
                    }
                }]
            }]
        }"#;
        let payload: WebhookPayload = serde_json::from_str(json).unwrap();
        let msgs = extract_text_messages(&payload);
        assert_eq!(msgs.len(), 1);
        assert_eq!(msgs[0].0, "15551234567");
        assert_eq!(msgs[0].1, "help");
    }

    #[test]
    fn extract_text_messages_ignores_non_text() {
        let json = r#"{
            "entry": [{
                "changes": [{
                    "value": {
                        "messages": [{
                            "from": "15551234567",
                            "type": "image",
                            "image": { "id": "img123" }
                        }],
                        "metadata": { "phone_number_id": "123456" }
                    }
                }]
            }]
        }"#;
        let payload: WebhookPayload = serde_json::from_str(json).unwrap();
        let msgs = extract_text_messages(&payload);
        assert!(msgs.is_empty());
    }

    #[test]
    fn extract_text_messages_handles_empty_payload() {
        let json = r#"{ "entry": [] }"#;
        let payload: WebhookPayload = serde_json::from_str(json).unwrap();
        let msgs = extract_text_messages(&payload);
        assert!(msgs.is_empty());
    }

    #[test]
    fn extract_text_messages_handles_multiple_messages() {
        let json = r#"{
            "entry": [{
                "changes": [{
                    "value": {
                        "messages": [
                            { "from": "111", "type": "text", "text": { "body": "status" } },
                            { "from": "222", "type": "text", "text": { "body": "help" } }
                        ],
                        "metadata": { "phone_number_id": "123456" }
                    }
                }]
            }]
        }"#;
        let payload: WebhookPayload = serde_json::from_str(json).unwrap();
        let msgs = extract_text_messages(&payload);
        assert_eq!(msgs.len(), 2);
        assert_eq!(msgs[0].1, "status");
        assert_eq!(msgs[1].1, "help");
    }

    #[tokio::test]
    async fn transport_send_message_calls_graph_api() {
        let mut server = mockito::Server::new_async().await;
        let mock = server
            .mock("POST", "/123456/messages")
            .match_header("authorization", "Bearer test-token")
            .with_body(r#"{"messages": [{"id": "wamid.abc123"}]}"#)
            .create_async()
            .await;

        let transport = WhatsAppTransport::with_api_base(
            "123456".to_string(),
            "test-token".to_string(),
            server.url(),
        );

        let result = transport
            .send_message("15551234567", "hello", "<p>hello</p>")
            .await;
        assert!(result.is_ok());
        assert_eq!(result.unwrap(), "wamid.abc123");
        mock.assert_async().await;
    }

    #[tokio::test]
    async fn transport_edit_sends_new_message() {
        let mut server = mockito::Server::new_async().await;
        let mock = server
            .mock("POST", "/123456/messages")
            .with_body(r#"{"messages": [{"id": "wamid.xyz"}]}"#)
            .create_async()
            .await;

        let transport = WhatsAppTransport::with_api_base(
            "123456".to_string(),
            "test-token".to_string(),
            server.url(),
        );

        let result = transport
            .edit_message("15551234567", "old-msg-id", "updated", "<p>updated</p>")
            .await;
        assert!(result.is_ok());
        mock.assert_async().await;
    }

    #[tokio::test]
    async fn transport_send_typing_succeeds() {
        let transport = WhatsAppTransport::new("123".to_string(), "tok".to_string());
        assert!(transport.send_typing("room1", true).await.is_ok());
        assert!(transport.send_typing("room1", false).await.is_ok());
    }

    #[tokio::test]
    async fn transport_handles_api_error() {
        let mut server = mockito::Server::new_async().await;
        server
            .mock("POST", "/123456/messages")
            .with_status(401)
            .with_body(r#"{"error": {"message": "Invalid token"}}"#)
            .create_async()
            .await;

        let transport = WhatsAppTransport::with_api_base(
            "123456".to_string(),
            "bad-token".to_string(),
            server.url(),
        );

        let result = transport
            .send_message("15551234567", "hello", "")
            .await;
        assert!(result.is_err());
        assert!(result.unwrap_err().contains("401"));
    }
}