package api

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"

	"git.quad4.io/quad4-software/osv-server/internal/config"
	"git.quad4.io/quad4-software/osv-server/internal/osv"
	"git.quad4.io/quad4-software/osv-server/internal/query"
)

// Server represents the HTTP API server.
type Server struct {
	router                 *chi.Mux
	osv                    *osv.Manager
	enableDownloadEndpoint bool
	silent                 bool
}

// NewServer creates a new API server instance.
func NewServer(osvManager *osv.Manager, cfg *config.Config) *Server {
	s := &Server{
		router:                 chi.NewRouter(),
		osv:                    osvManager,
		enableDownloadEndpoint: cfg.EnableDownloadEndpoint,
		silent:                 os.Getenv("OSV_SILENT") == "true",
	}

	s.setupRoutes()
	return s
}

func (s *Server) setupRoutes() {
	if !s.silent {
		s.router.Use(middleware.Logger)
	}
	s.router.Use(middleware.Recoverer)
	s.router.Use(middleware.RequestID)

	s.router.Get(RouteHealth, s.handleHealth)
	s.router.Get(RouteStats, s.handleStats)
	s.router.Get(RouteQuery, s.handleQuery)
	s.router.Post(RouteQuery, s.handleQueryPost)
	s.router.Get(RouteQueryBatch, s.handleQueryBatch)
	s.router.Post(RouteQueryBatch, s.handleQueryBatchPost)

	if s.enableDownloadEndpoint {
		s.router.Get(RouteDownload, s.handleDownload)
	}
}

func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	status := StatusHealthy
	if !s.osv.DataExists() {
		status = StatusInitializing
	}

	w.Header().Set("Content-Type", ContentTypeJSON)
	w.WriteHeader(http.StatusOK)
	// #nosec G104 - http.ResponseWriter.Write errors are rare and non-critical for health endpoint
	_, _ = w.Write([]byte(`{"status":"` + status + `"}`))
}

func (s *Server) handleStats(w http.ResponseWriter, r *http.Request) {
	stats := s.osv.GetStats()

	w.Header().Set("Content-Type", ContentTypeJSON)
	w.WriteHeader(http.StatusOK)

	json := `{
		"last_update": "` + stats.LastUpdate.Format(time.RFC3339) + `",
		"last_update_error": "` + stats.LastUpdateError + `",
		"total_downloads": ` + fmt.Sprintf("%d", stats.TotalDownloads) + `,
		"failed_downloads": ` + fmt.Sprintf("%d", stats.FailedDownloads) + `,
		"update_in_progress": ` + fmt.Sprintf("%t", stats.UpdateInProgress)

	if stats.DownloadProgress != nil {
		json += `,
		"download_progress": {
			"percent": ` + fmt.Sprintf("%.2f", stats.DownloadProgress.Percent) + `,
			"speed": "` + stats.DownloadProgress.Speed + `",
			"downloaded": ` + fmt.Sprintf("%d", stats.DownloadProgress.Downloaded) + `,
			"total": ` + fmt.Sprintf("%d", stats.DownloadProgress.Total) + `
		}`
	}

	json += `
	}`

	// #nosec G104 - http.ResponseWriter.Write errors are rare and non-critical for stats endpoint
	_, _ = w.Write([]byte(json))
}

func (s *Server) handleQuery(w http.ResponseWriter, r *http.Request) {
	if !s.osv.DataExists() {
		s.writeDownloadingResponse(w)
		return
	}

	dataPath := s.osv.GetDataPath()
	http.ServeFile(w, r, dataPath)
}

func (s *Server) handleQueryPost(w http.ResponseWriter, r *http.Request) {
	if !s.osv.DataExists() {
		s.writeDownloadingResponse(w)
		return
	}

	body, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, `{"error":"Failed to read request body"}`, http.StatusBadRequest)
		return
	}

	var req query.QueryRequest
	if err := json.Unmarshal(body, &req); err != nil {
		http.Error(w, `{"error":"Invalid JSON request"}`, http.StatusBadRequest)
		return
	}

	idx := s.osv.GetIndexer()
	resp, err := query.QueryDatabase(idx, &req)
	if err != nil {
		http.Error(w, fmt.Sprintf(`{"error":"%s"}`, err.Error()), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", ContentTypeJSON)
	w.WriteHeader(http.StatusOK)

	respJSON, err := json.Marshal(resp)
	if err != nil {
		http.Error(w, `{"error":"Failed to marshal response"}`, http.StatusInternalServerError)
		return
	}

	// #nosec G104 - http.ResponseWriter.Write errors are rare
	_, _ = w.Write(respJSON)
}

func (s *Server) handleQueryBatch(w http.ResponseWriter, r *http.Request) {
	if !s.osv.DataExists() {
		s.writeDownloadingResponse(w)
		return
	}

	dataPath := s.osv.GetDataPath()
	http.ServeFile(w, r, dataPath)
}

func (s *Server) handleQueryBatchPost(w http.ResponseWriter, r *http.Request) {
	if !s.osv.DataExists() {
		s.writeDownloadingResponse(w)
		return
	}

	body, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, `{"error":"Failed to read request body"}`, http.StatusBadRequest)
		return
	}

	var batchReq struct {
		Queries []query.QueryRequest `json:"queries"`
	}
	if err := json.Unmarshal(body, &batchReq); err != nil {
		http.Error(w, `{"error":"Invalid JSON request"}`, http.StatusBadRequest)
		return
	}

	idx := s.osv.GetIndexer()
	var results []query.QueryResponse

	for _, req := range batchReq.Queries {
		resp, err := query.QueryDatabase(idx, &req)
		if err != nil {
			http.Error(w, fmt.Sprintf(`{"error":"Query failed: %s"}`, err.Error()), http.StatusInternalServerError)
			return
		}
		results = append(results, *resp)
	}

	w.Header().Set("Content-Type", ContentTypeJSON)
	w.WriteHeader(http.StatusOK)

	response := struct {
		Results []query.QueryResponse `json:"results"`
	}{Results: results}

	respJSON, err := json.Marshal(response)
	if err != nil {
		http.Error(w, `{"error":"Failed to marshal response"}`, http.StatusInternalServerError)
		return
	}

	// #nosec G104 - http.ResponseWriter.Write errors are rare
	_, _ = w.Write(respJSON)
}

func (s *Server) handleDownload(w http.ResponseWriter, r *http.Request) {
	if !s.osv.DataExists() {
		s.writeDownloadingResponse(w)
		return
	}

	stats := s.osv.GetStats()
	if stats.UpdateInProgress {
		w.Header().Set("Content-Type", ContentTypeJSON)
		w.WriteHeader(http.StatusServiceUnavailable)
		// #nosec G104 - http.ResponseWriter.Write errors are rare
		_, _ = w.Write([]byte(`{"error":"Database update in progress, please try again later"}`))
		return
	}

	dataPath := s.osv.GetDataPath()
	meta, err := s.osv.GetMetadata()
	if err == nil && meta != nil {
		w.Header().Set("X-OSV-Hash", meta.Hash)
		w.Header().Set("X-OSV-Last-Modified", meta.LastModified.Format(time.RFC3339))
		w.Header().Set("X-OSV-Size", fmt.Sprintf("%d", meta.Size))
	}

	w.Header().Set("Content-Type", "application/zip")
	w.Header().Set("Content-Disposition", "attachment; filename=osv-database.zip")
	http.ServeFile(w, r, dataPath)
}

func (s *Server) writeDownloadingResponse(w http.ResponseWriter) {
	stats := s.osv.GetStats()
	w.Header().Set("Content-Type", ContentTypeJSON)
	w.WriteHeader(http.StatusServiceUnavailable)

	var message string
	if stats.DownloadProgress != nil {
		message = fmt.Sprintf(`"message":"Initial database download in progress: %.2f%% (%s/s)"`,
			stats.DownloadProgress.Percent, stats.DownloadProgress.Speed)
	} else {
		message = `"message":"Initial database download in progress"`
	}

	response := fmt.Sprintf(`{"error":"Data not available yet",%s,"status":"downloading"}`, message)
	// #nosec G104 - http.ResponseWriter.Write errors are rare
	_, _ = w.Write([]byte(response))
}

// ServeHTTP implements http.Handler.
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	s.router.ServeHTTP(w, r)
}