package httpapi

import (
	"context"
	"crypto/sha256"
	"crypto/subtle"
	"encoding/hex"
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"net/http"
	"strings"
	"time"

	"hopweb/internal/gitea"
	"hopweb/internal/store"
)

const maxWebhookBody = 2 << 20

type giteaClient interface {
	Repository(context.Context, string, string) (gitea.Repository, error)
}

type server struct {
	store         store.Store
	gitea         giteaClient
	adminToken    string
	webhookSecret string
	logger        *slog.Logger
}

func New(data store.Store, client giteaClient, adminToken, webhookSecret string, logger *slog.Logger) http.Handler {
	s := &server{store: data, gitea: client, adminToken: adminToken, webhookSecret: webhookSecret, logger: logger}
	mux := http.NewServeMux()
	mux.HandleFunc("GET /healthz", s.health)
	mux.HandleFunc("GET /readyz", s.ready)
	mux.Handle("GET /api/v1/repositories", s.requireAdmin(http.HandlerFunc(s.listRepositories)))
	mux.Handle("POST /api/v1/repositories/link", s.requireAdmin(http.HandlerFunc(s.linkRepository)))
	mux.HandleFunc("POST /api/v1/gitea/webhooks", s.giteaWebhook)
	return requestLogger(logger, mux)
}

func (s *server) health(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

func (s *server) ready(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
	defer cancel()
	if err := s.store.Ping(ctx); err != nil {
		writeError(w, http.StatusServiceUnavailable, "database unavailable")
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "ready"})
}

func (s *server) listRepositories(w http.ResponseWriter, r *http.Request) {
	repositories, err := s.store.ListRepositories(r.Context())
	if err != nil {
		s.logger.Error("list repositories", "error", err)
		writeError(w, http.StatusInternalServerError, "could not list repositories")
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"repositories": repositories})
}

func (s *server) linkRepository(w http.ResponseWriter, r *http.Request) {
	var input struct {
		Owner string `json:"owner"`
		Name  string `json:"name"`
	}
	if err := decodeJSON(w, r, &input); err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	if !validSlug(input.Owner) || !validSlug(input.Name) {
		writeError(w, http.StatusBadRequest, "owner and name are required and cannot contain slashes")
		return
	}
	repository, err := s.gitea.Repository(r.Context(), input.Owner, input.Name)
	if err != nil {
		if errors.Is(err, gitea.ErrTokenNotConfigured) {
			writeError(w, http.StatusServiceUnavailable, err.Error())
			return
		}
		s.logger.Warn("gitea repository lookup failed", "owner", input.Owner, "name", input.Name, "error", err)
		writeError(w, http.StatusBadGateway, "could not load repository from Gitea")
		return
	}
	saved, err := s.store.UpsertRepository(r.Context(), repository)
	if err != nil {
		s.logger.Error("link repository", "error", err)
		writeError(w, http.StatusInternalServerError, "could not link repository")
		return
	}
	writeJSON(w, http.StatusCreated, saved)
}

func (s *server) giteaWebhook(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, maxWebhookBody))
	if err != nil {
		writeError(w, http.StatusRequestEntityTooLarge, "webhook payload too large")
		return
	}
	if !gitea.VerifySignature(body, r.Header.Get("X-Gitea-Signature"), s.webhookSecret) {
		writeError(w, http.StatusUnauthorized, "invalid webhook signature")
		return
	}
	deliveryID := strings.TrimSpace(r.Header.Get("X-Gitea-Delivery"))
	event := strings.TrimSpace(r.Header.Get("X-Gitea-Event"))
	if deliveryID == "" || event == "" {
		writeError(w, http.StatusBadRequest, "missing Gitea delivery or event header")
		return
	}
	var payload struct {
		Repository *gitea.Repository `json:"repository"`
	}
	if err := json.Unmarshal(body, &payload); err != nil {
		writeError(w, http.StatusBadRequest, "invalid JSON payload")
		return
	}
	digest := sha256.Sum256(body)
	duplicate, err := s.store.RecordWebhook(r.Context(), store.WebhookDelivery{
		DeliveryID: deliveryID, Event: event, EventType: r.Header.Get("X-Gitea-Event-Type"),
		PayloadSHA256: hex.EncodeToString(digest[:]), Repository: payload.Repository,
	})
	if err != nil {
		s.logger.Error("record webhook", "delivery_id", deliveryID, "error", err)
		writeError(w, http.StatusInternalServerError, "could not record webhook")
		return
	}
	if duplicate {
		w.Header().Set("X-Hop-Duplicate", "true")
	}
	w.WriteHeader(http.StatusNoContent)
}

func (s *server) requireAdmin(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		authorization := r.Header.Get("Authorization")
		if !strings.HasPrefix(authorization, "Bearer ") {
			writeError(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		provided := strings.TrimPrefix(authorization, "Bearer ")
		if len(provided) != len(s.adminToken) || subtle.ConstantTimeCompare([]byte(provided), []byte(s.adminToken)) != 1 {
			writeError(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		next.ServeHTTP(w, r)
	})
}

func validSlug(value string) bool {
	value = strings.TrimSpace(value)
	return value != "" && !strings.ContainsAny(value, "/\\")
}

func decodeJSON(w http.ResponseWriter, r *http.Request, target any) error {
	r.Body = http.MaxBytesReader(w, r.Body, 64<<10)
	decoder := json.NewDecoder(r.Body)
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(target); err != nil {
		return errors.New("invalid JSON body")
	}
	if err := decoder.Decode(&struct{}{}); err != io.EOF {
		return errors.New("request body must contain one JSON object")
	}
	return nil
}

func writeError(w http.ResponseWriter, status int, message string) {
	writeJSON(w, status, map[string]any{"error": map[string]string{"message": message}})
}

func writeJSON(w http.ResponseWriter, status int, body any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(body)
}

func requestLogger(logger *slog.Logger, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		started := time.Now()
		next.ServeHTTP(w, r)
		logger.Info("request", "method", r.Method, "path", r.URL.Path, "duration_ms", time.Since(started).Milliseconds())
	})
}