package webhook

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"strings"

	"forgejo.riotpiao.com/rock/homelab-frontend/internal/notification"
)

// ForgejoHandler receives Forgejo webhook payloads and forwards them to Gotify.
// Forgejo sends a Gitea-compatible JSON payload with X-Gitea-Signature-256 header.
type ForgejoHandler struct {
	secret string
	gotify *notification.GotifyClient
}

// NewForgejoHandler creates a handler from environment variables.
// Required: GOTIFY_URL, GOTIFY_APP_TOKEN
// Optional: FORGEJO_WEBHOOK_SECRET (if empty, HMAC verification is skipped)
func NewForgejoHandler() *ForgejoHandler {
	gotifyURL := os.Getenv("GOTIFY_URL")
	appToken := os.Getenv("GOTIFY_APP_TOKEN")

	var client *notification.GotifyClient
	if gotifyURL != "" && appToken != "" {
		client = notification.NewGotifyClient(gotifyURL, appToken, "")
	}

	return &ForgejoHandler{
		secret: os.Getenv("FORGEJO_WEBHOOK_SECRET"),
		gotify: client,
	}
}

// ServeHTTP handles POST /v1/webhooks/forgejo
func (h *ForgejoHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20)) // 1MB limit
	if err != nil {
		http.Error(w, "failed to read body", http.StatusBadRequest)
		return
	}

	// Verify HMAC if secret is set
	if h.secret != "" {
		sig := r.Header.Get("X-Gitea-Signature-256")
		if sig == "" {
			sig = r.Header.Get("X-Hub-Signature-256")
		}
		if !h.verifySignature(body, sig) {
			http.Error(w, "invalid signature", http.StatusForbidden)
			return
		}
	}

	if h.gotify == nil {
		log.Printf("forgejo webhook received but Gotify not configured (GOTIFY_URL/GOTIFY_APP_TOKEN missing)")
		w.WriteHeader(http.StatusOK)
		return
	}

	event := r.Header.Get("X-Gitea-Event")
	if event == "" {
		event = r.Header.Get("X-GitHub-Event")
	}

	title, message, priority := h.formatMessage(event, body)
	if title == "" {
		// Unhandled event type — ack and ignore
		w.WriteHeader(http.StatusOK)
		return
	}

	msg := notification.GotifyMessage{
		Title:    title,
		Message:  message,
		Priority: priority,
	}

	if _, err := h.gotify.SendMessage(msg); err != nil {
		log.Printf("forgejo webhook: failed to send gotify message: %v", err)
		http.Error(w, "failed to send notification", http.StatusBadGateway)
		return
	}

	log.Printf("forgejo webhook: sent gotify notification event=%s title=%q", event, title)
	w.WriteHeader(http.StatusOK)
}

// verifySignature checks X-Gitea-Signature-256: sha256=<hex>
func (h *ForgejoHandler) verifySignature(body []byte, sig string) bool {
	sig = strings.TrimPrefix(sig, "sha256=")
	if sig == "" {
		return false
	}
	mac := hmac.New(sha256.New, []byte(h.secret))
	mac.Write(body)
	expected := hex.EncodeToString(mac.Sum(nil))
	return hmac.Equal([]byte(sig), []byte(expected))
}

// formatMessage converts a Forgejo event payload into a Gotify title + message.
// Returns empty title if the event should be ignored.
func (h *ForgejoHandler) formatMessage(event string, body []byte) (title, message string, priority int) {
	var payload map[string]interface{}
	if err := json.Unmarshal(body, &payload); err != nil {
		return "", "", 0
	}

	repo := jsonStr(payload, "repository", "full_name")
	sender := jsonStr(payload, "sender", "login")

	switch event {
	case "push":
		ref := strings.TrimPrefix(fmt.Sprintf("%v", payload["ref"]), "refs/heads/")
		commits, _ := payload["commits"].([]interface{})
		count := len(commits)
		commitMsg := ""
		if count > 0 {
			if c, ok := commits[0].(map[string]interface{}); ok {
				commitMsg = fmt.Sprintf("%v", c["message"])
				// truncate long commit messages
				if len(commitMsg) > 80 {
					commitMsg = commitMsg[:80] + "…"
				}
			}
		}
		return fmt.Sprintf("📦 %s", repo),
			fmt.Sprintf("%s pushed %d commit(s) to %s\n%s", sender, count, ref, commitMsg),
			5

	case "pull_request":
		action := fmt.Sprintf("%v", payload["action"])
		if action != "opened" && action != "closed" && action != "reopened" && action != "merged" {
			return "", "", 0 // ignore noise (labeled, assigned, etc.)
		}
		pr, _ := payload["pull_request"].(map[string]interface{})
		number := fmt.Sprintf("%v", pr["number"])
		prTitle := fmt.Sprintf("%v", pr["title"])
		merged, _ := pr["merged"].(bool)
		if action == "closed" && merged {
			action = "merged"
		}
		return fmt.Sprintf("🔀 PR #%s %s — %s", number, action, repo),
			fmt.Sprintf("%s: %s\nby %s", action, prTitle, sender),
			5

	case "issues":
		action := fmt.Sprintf("%v", payload["action"])
		if action != "opened" && action != "closed" && action != "reopened" {
			return "", "", 0
		}
		issue, _ := payload["issue"].(map[string]interface{})
		number := fmt.Sprintf("%v", issue["number"])
		issueTitle := fmt.Sprintf("%v", issue["title"])
		return fmt.Sprintf("🐛 Issue #%s %s — %s", number, action, repo),
			fmt.Sprintf("%s: %s\nby %s", action, issueTitle, sender),
			4

	case "issue_comment", "pull_request_review_comment":
		issue, _ := payload["issue"].(map[string]interface{})
		comment, _ := payload["comment"].(map[string]interface{})
		number := fmt.Sprintf("%v", issue["number"])
		body := fmt.Sprintf("%v", comment["body"])
		if len(body) > 100 {
			body = body[:100] + "…"
		}
		return fmt.Sprintf("💬 Comment on #%s — %s", number, repo),
			fmt.Sprintf("%s: %s", sender, body),
			3

	case "release":
		action := fmt.Sprintf("%v", payload["action"])
		if action != "published" {
			return "", "", 0
		}
		release, _ := payload["release"].(map[string]interface{})
		tag := fmt.Sprintf("%v", release["tag_name"])
		name := fmt.Sprintf("%v", release["name"])
		return fmt.Sprintf("🚀 Release %s — %s", tag, repo),
			fmt.Sprintf("%s published by %s", name, sender),
			7

	default:
		return "", "", 0
	}
}

// jsonStr safely traverses nested map keys.
func jsonStr(m map[string]interface{}, keys ...string) string {
	cur := m
	for i, k := range keys {
		v, ok := cur[k]
		if !ok {
			return ""
		}
		if i == len(keys)-1 {
			return fmt.Sprintf("%v", v)
		}
		cur, ok = v.(map[string]interface{})
		if !ok {
			return ""
		}
	}
	return ""
}