use std::sync::Arc;

use axum::body::Bytes;
use axum::extract::Extension;
use axum::http::{HeaderMap, StatusCode};
use hmac::{Hmac, Mac};
use secrecy::ExposeSecret;
use sha2::Sha256;

use compliance_core::models::ScanTrigger;

use crate::agent::ComplianceAgent;

type HmacSha256 = Hmac<Sha256>;

pub async fn handle_github_webhook(
    Extension(agent): Extension<Arc<ComplianceAgent>>,
    headers: HeaderMap,
    body: Bytes,
) -> StatusCode {
    // Verify HMAC signature
    if let Some(secret) = &agent.config.github_webhook_secret {
        let signature = headers
            .get("x-hub-signature-256")
            .and_then(|v| v.to_str().ok())
            .unwrap_or("");

        if !verify_signature(secret.expose_secret(), &body, signature) {
            tracing::warn!("GitHub webhook: invalid signature");
            return StatusCode::UNAUTHORIZED;
        }
    }

    let event = headers
        .get("x-github-event")
        .and_then(|v| v.to_str().ok())
        .unwrap_or("");

    let payload: serde_json::Value = match serde_json::from_slice(&body) {
        Ok(v) => v,
        Err(e) => {
            tracing::warn!("GitHub webhook: invalid JSON: {e}");
            return StatusCode::BAD_REQUEST;
        }
    };

    match event {
        "push" => handle_push(agent, &payload).await,
        "pull_request" => handle_pull_request(agent, &payload).await,
        _ => {
            tracing::debug!("GitHub webhook: ignoring event '{event}'");
            StatusCode::OK
        }
    }
}

async fn handle_push(agent: Arc<ComplianceAgent>, payload: &serde_json::Value) -> StatusCode {
    let repo_url = payload["repository"]["clone_url"]
        .as_str()
        .or_else(|| payload["repository"]["html_url"].as_str())
        .unwrap_or("");

    if repo_url.is_empty() {
        return StatusCode::BAD_REQUEST;
    }

    // Find matching tracked repository
    let repo = agent
        .db
        .repositories()
        .find_one(mongodb::bson::doc! { "git_url": repo_url })
        .await
        .ok()
        .flatten();

    if let Some(repo) = repo {
        let repo_id = repo.id.map(|id| id.to_hex()).unwrap_or_default();
        let agent_clone = (*agent).clone();
        tokio::spawn(async move {
            tracing::info!("GitHub push webhook: triggering scan for {repo_id}");
            if let Err(e) = agent_clone.run_scan(&repo_id, ScanTrigger::Webhook).await {
                tracing::error!("Webhook-triggered scan failed: {e}");
            }
        });
    } else {
        tracing::debug!("GitHub push webhook: no tracked repo for {repo_url}");
    }

    StatusCode::OK
}

async fn handle_pull_request(
    agent: Arc<ComplianceAgent>,
    payload: &serde_json::Value,
) -> StatusCode {
    let action = payload["action"].as_str().unwrap_or("");
    if action != "opened" && action != "synchronize" {
        return StatusCode::OK;
    }

    let repo_url = payload["repository"]["clone_url"].as_str().unwrap_or("");
    let pr_number = payload["pull_request"]["number"].as_u64().unwrap_or(0);
    let head_sha = payload["pull_request"]["head"]["sha"]
        .as_str()
        .unwrap_or("");
    let base_sha = payload["pull_request"]["base"]["sha"]
        .as_str()
        .unwrap_or("");

    if repo_url.is_empty() || pr_number == 0 || head_sha.is_empty() || base_sha.is_empty() {
        return StatusCode::BAD_REQUEST;
    }

    let repo = agent
        .db
        .repositories()
        .find_one(mongodb::bson::doc! { "git_url": repo_url })
        .await
        .ok()
        .flatten();

    if let Some(repo) = repo {
        let repo_id = repo.id.map(|id| id.to_hex()).unwrap_or_default();
        let head_sha = head_sha.to_string();
        let base_sha = base_sha.to_string();
        let agent_clone = (*agent).clone();
        tokio::spawn(async move {
            tracing::info!("GitHub PR webhook: reviewing PR #{pr_number} on {repo_id}");
            if let Err(e) = agent_clone
                .run_pr_review(&repo_id, pr_number, &base_sha, &head_sha)
                .await
            {
                tracing::error!("PR review failed for #{pr_number}: {e}");
            }
        });
    } else {
        tracing::debug!("GitHub PR webhook: no tracked repo for {repo_url}");
    }

    StatusCode::OK
}

fn verify_signature(secret: &str, body: &[u8], signature: &str) -> bool {
    let sig = signature.strip_prefix("sha256=").unwrap_or(signature);
    let sig_bytes = match hex::decode(sig) {
        Ok(b) => b,
        Err(_) => return false,
    };

    let mut mac = match HmacSha256::new_from_slice(secret.as_bytes()) {
        Ok(m) => m,
        Err(_) => return false,
    };
    mac.update(body);
    mac.verify_slice(&sig_bytes).is_ok()
}