package handlers

import (
	"encoding/json"
	"io"
	"net/http"

	"github.com/go-chi/chi"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/delivery"
)

const (
	// maxWebhookBodySize is the maximum allowed webhook request body (1 MB).
	maxWebhookBodySize = 1 << 20
)

// HandleWebhook handles incoming webhook requests at entrypoint URLs.
// Only POST requests are accepted; all other methods return 405 Method Not Allowed.
// Events and deliveries are stored in the per-webhook database.
func (h *Handlers) HandleWebhook() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			w.Header().Set("Allow", "POST")
			http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
			return
		}

		entrypointUUID := chi.URLParam(r, "uuid")
		if entrypointUUID == "" {
			http.NotFound(w, r)
			return
		}

		h.log.Info("webhook request received",
			"entrypoint_uuid", entrypointUUID,
			"method", r.Method,
			"remote_addr", r.RemoteAddr,
		)

		// Look up entrypoint by path (from main application DB)
		var entrypoint database.Entrypoint
		result := h.db.DB().Where("path = ?", entrypointUUID).First(&entrypoint)
		if result.Error != nil {
			h.log.Debug("entrypoint not found", "path", entrypointUUID)
			http.NotFound(w, r)
			return
		}

		// Check if active
		if !entrypoint.Active {
			http.Error(w, "Gone", http.StatusGone)
			return
		}

		// Read body with size limit
		body, err := io.ReadAll(io.LimitReader(r.Body, maxWebhookBodySize+1))
		if err != nil {
			h.log.Error("failed to read request body", "error", err)
			http.Error(w, "Bad request", http.StatusBadRequest)
			return
		}
		if len(body) > maxWebhookBodySize {
			http.Error(w, "Request body too large", http.StatusRequestEntityTooLarge)
			return
		}

		// Serialize headers as JSON
		headersJSON, err := json.Marshal(r.Header)
		if err != nil {
			h.log.Error("failed to serialize headers", "error", err)
			http.Error(w, "Internal server error", http.StatusInternalServerError)
			return
		}

		// Find all active targets for this webhook (from main application DB)
		var targets []database.Target
		if targetErr := h.db.DB().Where("webhook_id = ? AND active = ?", entrypoint.WebhookID, true).Find(&targets).Error; targetErr != nil {
			h.log.Error("failed to query targets", "error", targetErr)
			http.Error(w, "Internal server error", http.StatusInternalServerError)
			return
		}

		// Get the per-webhook database for event storage
		webhookDB, err := h.dbMgr.GetDB(entrypoint.WebhookID)
		if err != nil {
			h.log.Error("failed to get webhook database",
				"webhook_id", entrypoint.WebhookID,
				"error", err,
			)
			http.Error(w, "Internal server error", http.StatusInternalServerError)
			return
		}

		// Create the event and deliveries in a transaction on the per-webhook DB
		tx := webhookDB.Begin()
		if tx.Error != nil {
			h.log.Error("failed to begin transaction", "error", tx.Error)
			http.Error(w, "Internal server error", http.StatusInternalServerError)
			return
		}

		event := &database.Event{
			WebhookID:    entrypoint.WebhookID,
			EntrypointID: entrypoint.ID,
			Method:       r.Method,
			Headers:      string(headersJSON),
			Body:         string(body),
			ContentType:  r.Header.Get("Content-Type"),
		}

		if err := tx.Create(event).Error; err != nil {
			tx.Rollback()
			h.log.Error("failed to create event", "error", err)
			http.Error(w, "Internal server error", http.StatusInternalServerError)
			return
		}

		// Create delivery records for each active target
		for i := range targets {
			dlv := &database.Delivery{
				EventID:  event.ID,
				TargetID: targets[i].ID,
				Status:   database.DeliveryStatusPending,
			}
			if err := tx.Create(dlv).Error; err != nil {
				tx.Rollback()
				h.log.Error("failed to create delivery",
					"target_id", targets[i].ID,
					"error", err,
				)
				http.Error(w, "Internal server error", http.StatusInternalServerError)
				return
			}
		}

		if err := tx.Commit().Error; err != nil {
			h.log.Error("failed to commit transaction", "error", err)
			http.Error(w, "Internal server error", http.StatusInternalServerError)
			return
		}

		// Notify the delivery engine with inline event data so it can
		// process deliveries immediately without a DB round-trip.
		// Large bodies (>= 16KB) are left nil to keep channel memory
		// bounded; the engine fetches them from DB on demand.
		n := delivery.Notification{
			WebhookID:   entrypoint.WebhookID,
			EventID:     event.ID,
			Method:      event.Method,
			Headers:     event.Headers,
			ContentType: event.ContentType,
		}
		bodyStr := string(body)
		if len(body) < delivery.MaxInlineBodySize {
			n.Body = &bodyStr
		}
		h.notifier.Notify(n)

		h.log.Info("webhook event created",
			"event_id", event.ID,
			"webhook_id", entrypoint.WebhookID,
			"entrypoint_id", entrypoint.ID,
			"target_count", len(targets),
		)

		w.WriteHeader(http.StatusOK)
		if _, err := w.Write([]byte(`{"status":"ok"}`)); err != nil {
			h.log.Error("failed to write response", "error", err)
		}
	}
}