package api

import (
	"net/http"
	"strconv"
	"strings"

	"bat-api/internal/backendrpc"
)

func (s *Server) handleReleaseList(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeErrorJSON(w, http.StatusMethodNotAllowed, "method_not_allowed", "method not allowed")
		return
	}
	backend, ok := s.backend.(ReleaseBackend)
	if !ok || backend == nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "release_backend_unavailable", "Rust bat release backend is unavailable")
		return
	}
	channel := r.URL.Query().Get("channel")
	result, err := backend.ReleaseList(r.Context(), backendrpc.ReleaseListParams{Channel: channel})
	if err != nil {
		s.writeControlBackendError(w, "release-list", err)
		return
	}
	writeNoStoreJSON(w, http.StatusOK, result)
}

func (s *Server) handleReleaseDistribution(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeErrorJSON(w, http.StatusMethodNotAllowed, "method_not_allowed", "method not allowed")
		return
	}
	channel, releaseID, err := releaseSelector(r)
	if err != nil {
		writeErrorJSON(w, http.StatusBadRequest, "invalid_release_selector", err.Error())
		return
	}
	params, err := releaseDistributionParams(r, channel, releaseID)
	if err != nil {
		writeErrorJSON(w, http.StatusBadRequest, "invalid_release_query", err.Error())
		return
	}
	page, err := s.requestReleaseDistribution(r, params)
	if err != nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "release_backend_unavailable", err.Error())
		return
	}
	if page == nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "release_backend_unavailable", "Rust release distribution returned no result")
		return
	}
	status := http.StatusOK
	if !page.Available {
		status = http.StatusConflict
	}
	writeNoStoreJSON(w, status, page)
}

func (s *Server) handleAdminReleaseStatus(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet && r.Method != http.MethodHead {
		writeErrorJSON(w, http.StatusMethodNotAllowed, "method_not_allowed", "method not allowed")
		return
	}
	if !s.requireAdminToken(w, r) {
		return
	}
	backend, ok := s.backend.(ReleaseBackend)
	if !ok || backend == nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "release_backend_unavailable", "Rust bat release backend is unavailable")
		return
	}
	result, err := backend.ReleaseStatus(r.Context())
	if err != nil {
		s.writeControlBackendError(w, "release-status", err)
		return
	}
	if r.Method == http.MethodHead {
		w.Header().Set("Cache-Control", "no-store")
		w.WriteHeader(http.StatusOK)
		return
	}
	writeNoStoreJSON(w, http.StatusOK, result)
}

func (s *Server) handleAdminReleaseList(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet && r.Method != http.MethodHead {
		writeErrorJSON(w, http.StatusMethodNotAllowed, "method_not_allowed", "method not allowed")
		return
	}
	if !s.requireAdminToken(w, r) {
		return
	}
	backend, ok := s.backend.(ReleaseBackend)
	if !ok || backend == nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "release_backend_unavailable", "Rust bat release backend is unavailable")
		return
	}
	result, err := backend.ReleaseList(r.Context(), backendrpc.ReleaseListParams{
		Channel: r.URL.Query().Get("channel"),
	})
	if err != nil {
		s.writeControlBackendError(w, "release-list", err)
		return
	}
	if r.Method == http.MethodHead {
		w.Header().Set("Cache-Control", "no-store")
		w.WriteHeader(http.StatusOK)
		return
	}
	writeNoStoreJSON(w, http.StatusOK, result)
}

func releaseSelector(r *http.Request) (string, string, error) {
	channel := strings.TrimSpace(r.URL.Query().Get("channel"))
	releaseID := strings.TrimSpace(r.URL.Query().Get("release_id"))
	if channel == "" {
		channel = "official"
	}
	if channel != "official" && channel != "localized" {
		return "", "", &releaseSelectorError{message: "channel must be official or localized"}
	}
	if releaseID == "." || releaseID == ".." ||
		strings.Contains(releaseID, "/") ||
		strings.Contains(releaseID, "\\") ||
		strings.Contains(releaseID, ":") ||
		strings.ContainsRune(releaseID, 0) {
		return "", "", &releaseSelectorError{message: "release_id contains an unsafe path character"}
	}
	return channel, releaseID, nil
}

type releaseSelectorError struct {
	message string
}

func (e *releaseSelectorError) Error() string {
	return e.message
}

func (s *Server) loadReleaseDistribution(r *http.Request, channel, releaseID, destination string) (*backendrpc.ReleaseDistributionPage, error) {
	return s.loadReleaseDistributionFrom(r, backendrpc.ReleaseDistributionParams{
		Channel:     channel,
		ReleaseID:   releaseID,
		Destination: destination,
		Offset:      0,
		Limit:       1000,
	})
}

func releaseDistributionParams(r *http.Request, channel, releaseID string) (backendrpc.ReleaseDistributionParams, error) {
	params := backendrpc.ReleaseDistributionParams{
		Channel:   channel,
		ReleaseID: releaseID,
	}
	query := r.URL.Query()
	if destination := strings.TrimSpace(query.Get("destination")); destination != "" {
		params.Destination = destination
	}
	if raw := strings.TrimSpace(query.Get("offset")); raw != "" {
		offset, err := strconv.ParseUint(raw, 10, 64)
		if err != nil || uint64(int(^uint(0)>>1)) < offset {
			return backendrpc.ReleaseDistributionParams{}, &releaseSelectorError{
				message: "offset must be a non-negative integer",
			}
		}
		params.Offset = int(offset)
	}
	if raw := strings.TrimSpace(query.Get("limit")); raw != "" {
		limit, err := strconv.ParseUint(raw, 10, 64)
		if err != nil || limit == 0 || limit > 1000 {
			return backendrpc.ReleaseDistributionParams{}, &releaseSelectorError{
				message: "limit must be in 1..=1000",
			}
		}
		params.Limit = int(limit)
	}
	return params, nil
}

func (s *Server) requestReleaseDistribution(r *http.Request, params backendrpc.ReleaseDistributionParams) (*backendrpc.ReleaseDistributionPage, error) {
	backend, ok := s.backend.(ReleaseBackend)
	if !ok || backend == nil {
		return nil, &releaseSelectorError{message: "Rust bat release backend is unavailable"}
	}
	return backend.ReleaseDistribution(r.Context(), params)
}

func (s *Server) loadReleaseDistributionFrom(r *http.Request, params backendrpc.ReleaseDistributionParams) (*backendrpc.ReleaseDistributionPage, error) {
	backend, ok := s.backend.(ReleaseBackend)
	if !ok || backend == nil {
		return nil, &releaseSelectorError{message: "Rust bat release backend is unavailable"}
	}
	pageSize := 1000
	result, err := backend.ReleaseDistribution(r.Context(), params)
	if err != nil || result == nil || !result.Available {
		return result, err
	}
	if params.Destination != "" {
		if result.Total != 1 || result.Offset != 0 || result.Limit != 1 || len(result.Entries) != 1 {
			return nil, &releaseSelectorError{message: "Rust single-entry release distribution response is invalid"}
		}
		return result, nil
	}
	if result.Total <= len(result.Entries) {
		return result, nil
	}
	all := append([]backendrpc.ReleaseDistributionEntry(nil), result.Entries...)
	for offset := len(all); offset < result.Total; {
		next, nextErr := backend.ReleaseDistribution(r.Context(), backendrpc.ReleaseDistributionParams{
			Channel:     params.Channel,
			ReleaseID:   params.ReleaseID,
			Destination: params.Destination,
			Offset:      offset,
			Limit:       pageSize,
		})
		if nextErr != nil {
			return nil, nextErr
		}
		if next == nil || !next.Available || len(next.Entries) == 0 {
			return nil, &releaseSelectorError{message: "Rust release distribution page is incomplete"}
		}
		all = append(all, next.Entries...)
		offset = len(all)
		if len(all) > result.Total {
			all = all[:result.Total]
			break
		}
	}
	result.Entries = all
	result.Offset = 0
	result.Limit = len(all)
	return result, nil
}

func releaseDistributionEntry(page *backendrpc.ReleaseDistributionPage, rel string) (ResourceEntry, bool) {
	rel = strings.TrimPrefix(strings.ReplaceAll(rel, "\\", "/"), "/")
	for _, entry := range page.Entries {
		destination := strings.TrimPrefix(strings.ReplaceAll(entry.Destination, "\\", "/"), "/")
		if destination == rel {
			return ResourceEntry{
				URL:          entry.URL,
				RelativePath: destination,
				Bytes:        entry.Bytes,
				BLAKE3:       entry.BLAKE3,
				Present:      true,
				SizeMatch:    true,
			}, true
		}
	}
	return ResourceEntry{}, false
}