package httpapi

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"strings"
	"time"

	"supply-intelligence/internal/admission"
	"supply-intelligence/internal/discovery"
	"supply-intelligence/internal/domain"
	"supply-intelligence/internal/gatewayconsumer"
	"supply-intelligence/internal/probe"
	"supply-intelligence/internal/publish"
	"supply-intelligence/internal/repository"
)

type Server struct {
	repo                   *repository.MemoryRepository
	probeService           *probe.Service
	publishService         *publish.Service
	gatewayConsumerService *gatewayconsumer.Service
	discoveryService       *discovery.Service
	admissionService       *admission.Service
}

type packageChangesResponse struct {
	Items      []domain.PackageChangeEvent `json:"items"`
	NextCursor string                      `json:"next_cursor"`
}

type discoveryCandidatesResponse struct {
	Items []domain.DiscoveryCandidate `json:"items"`
}

func NewServer(repo *repository.MemoryRepository, probeService *probe.Service, publishService *publish.Service, gatewayConsumerService *gatewayconsumer.Service, discoveryService *discovery.Service, admissionService *admission.Service) *Server {
	return &Server{repo: repo, probeService: probeService, publishService: publishService, gatewayConsumerService: gatewayConsumerService, discoveryService: discoveryService, admissionService: admissionService}
}

func (s *Server) Routes() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/healthz", s.handleHealth)
	mux.HandleFunc("/internal/supply-intelligence/accounts/", s.handleGetRoutingState)
	mux.HandleFunc("/internal/supply-intelligence/probe/evaluate", s.handleEvaluateProbe)
	mux.HandleFunc("/internal/supply-intelligence/publish/package-event", s.handlePublishPackageEvent)
	mux.HandleFunc("/internal/supply-intelligence/discovery/candidates", s.handleDiscoveryCandidates)
	mux.HandleFunc("/internal/supply-intelligence/gateway/package-changes", s.handleListPackageChanges)
	mux.HandleFunc("/internal/supply-intelligence/gateway/package-changes/", s.handleAckPackageChange)
	mux.HandleFunc("/internal/supply-intelligence/gateway/consume-once", s.handleConsumeOnce)
	mux.HandleFunc("/internal/supply-intelligence/admission/run", s.handleAdmissionRun)
	mux.HandleFunc("/internal/supply-intelligence/admission/candidates", s.handleAdmissionCandidates)
	return mux
}

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

func (s *Server) handleGetRoutingState(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
		return
	}
	prefix := "/internal/supply-intelligence/accounts/"
	path := strings.TrimPrefix(r.URL.Path, prefix)
	if !strings.HasSuffix(path, "/routing-state") {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not_found"})
		return
	}
	accountIDPart := strings.TrimSuffix(path, "/routing-state")
	var accountID int64
	if _, err := parseInt64(accountIDPart, &accountID); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_account_id"})
		return
	}
	state, ok := s.repo.GetRoutingState(accountID)
	if !ok {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not_found"})
		return
	}
	writeJSON(w, http.StatusOK, state)
}

func (s *Server) handleEvaluateProbe(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
		return
	}
	if s.probeService == nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "probe_service_unavailable"})
		return
	}

	var payload struct {
		AccountID      int64  `json:"account_id"`
		Platform       string `json:"platform"`
		CurrentStatus  string `json:"current_status"`
		StatusCode     int    `json:"status_code"`
		TransportError string `json:"transport_error"`
	}
	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_json"})
		return
	}
	if payload.AccountID <= 0 {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_account_id"})
		return
	}
	if payload.Platform == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing_platform"})
		return
	}
	if payload.CurrentStatus == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing_current_status"})
		return
	}

	var transportErr error
	if payload.TransportError != "" {
		transportErr = errors.New(payload.TransportError)
	}

	result, err := s.probeService.EvaluateHTTPResult(context.Background(), probe.EvaluateInput{
		AccountID:      payload.AccountID,
		Platform:       payload.Platform,
		CurrentStatus:  domainAccountStatus(payload.CurrentStatus),
		StatusCode:     payload.StatusCode,
		TransportError: transportErr,
	})
	if err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()})
		return
	}
	writeJSON(w, http.StatusOK, result)
}

func (s *Server) handlePublishPackageEvent(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
		return
	}
	if s.publishService == nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "publish_service_unavailable"})
		return
	}

	var payload struct {
		EventID    string `json:"event_id"`
		PackageID  int64  `json:"package_id"`
		Platform   string `json:"platform"`
		Model      string `json:"model"`
		Version    int64  `json:"version"`
		OccurredAt string `json:"occurred_at"`
	}
	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_json"})
		return
	}

	var occurredAt time.Time
	if payload.OccurredAt != "" {
		parsed, err := time.Parse(time.RFC3339, payload.OccurredAt)
		if err != nil {
			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_occurred_at"})
			return
		}
		occurredAt = parsed
	}

	event, err := s.publishService.RecordPackagePublished(r.Context(), publish.RecordPackagePublishedInput{
		EventID:    payload.EventID,
		PackageID:  payload.PackageID,
		Platform:   payload.Platform,
		Model:      payload.Model,
		Version:    payload.Version,
		OccurredAt: occurredAt,
	})
	if err != nil {
		if errors.Is(err, publish.ErrInvalidPublishInput) {
			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_publish_input"})
			return
		}
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "internal_error"})
		return
	}
	writeJSON(w, http.StatusOK, event)
}

func (s *Server) handleDiscoveryCandidates(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodPost:
		s.handleCreateDiscoveryCandidate(w, r)
	case http.MethodGet:
		s.handleListDiscoveryCandidates(w, r)
	default:
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
	}
}

func (s *Server) handleCreateDiscoveryCandidate(w http.ResponseWriter, r *http.Request) {
	if s.discoveryService == nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "discovery_service_unavailable"})
		return
	}
	var payload struct {
		CandidateID  string `json:"candidate_id"`
		AccountID    int64  `json:"account_id"`
		Platform     string `json:"platform"`
		Model        string `json:"model"`
		Source       string `json:"source"`
		ReasonCode   string `json:"reason_code"`
		DiscoveredAt string `json:"discovered_at"`
	}
	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_json"})
		return
	}
	var discoveredAt time.Time
	if strings.TrimSpace(payload.DiscoveredAt) != "" {
		parsed, err := time.Parse(time.RFC3339, payload.DiscoveredAt)
		if err != nil {
			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_discovered_at"})
			return
		}
		discoveredAt = parsed
	}
	out, err := s.discoveryService.RecordCandidate(r.Context(), discovery.RecordCandidateInput{
		CandidateID:  payload.CandidateID,
		AccountID:    payload.AccountID,
		Platform:     payload.Platform,
		Model:        payload.Model,
		Source:       payload.Source,
		ReasonCode:   payload.ReasonCode,
		DiscoveredAt: discoveredAt,
	})
	if err != nil {
		if errors.Is(err, discovery.ErrInvalidCandidateInput) {
			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_candidate_input"})
			return
		}
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "internal_error"})
		return
	}
	writeJSON(w, http.StatusOK, out)
}

func (s *Server) handleListDiscoveryCandidates(w http.ResponseWriter, r *http.Request) {
	if s.discoveryService == nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "discovery_service_unavailable"})
		return
	}
	status, ok := parseDiscoveryCandidateStatus(strings.TrimSpace(r.URL.Query().Get("status")))
	if !ok {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_status"})
		return
	}
	writeJSON(w, http.StatusOK, discoveryCandidatesResponse{Items: s.discoveryService.ListCandidates(r.Context(), status)})
}

func parseDiscoveryCandidateStatus(raw string) (domain.DiscoveryCandidateStatus, bool) {
	if raw == "" {
		return "", true
	}
	status := domain.DiscoveryCandidateStatus(raw)
	switch status {
	case domain.DiscoveryCandidateStatusPendingAdmission, domain.DiscoveryCandidateStatusAdmitted, domain.DiscoveryCandidateStatusRejected:
		return status, true
	default:
		return "", false
	}
}

func (s *Server) handleListPackageChanges(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
		return
	}
	items, nextCursor := s.repo.ListPackageEventsAfter(strings.TrimSpace(r.URL.Query().Get("cursor")))
	writeJSON(w, http.StatusOK, packageChangesResponse{Items: items, NextCursor: nextCursor})
}

func (s *Server) handleAckPackageChange(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
		return
	}
	prefix := "/internal/supply-intelligence/gateway/package-changes/"
	path := strings.TrimPrefix(r.URL.Path, prefix)
	if !strings.HasSuffix(path, "/ack") {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not_found"})
		return
	}
	eventID := strings.TrimSuffix(path, "/ack")
	var payload struct {
		Consumer string `json:"consumer"`
		Result   string `json:"result"`
		Detail   string `json:"detail"`
	}
	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_json"})
		return
	}
	ackResult := domain.GatewayAckResult(payload.Result)
	if !repository.IsGatewayAckResult(ackResult) {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_result"})
		return
	}
	consumer := strings.TrimSpace(payload.Consumer)
	if consumer == "" {
		consumer = "gateway"
	}
	_, err := s.repo.AckPackageEvent(eventID, consumer, ackResult, payload.Detail, time.Now().UTC())
	if err != nil {
		if errors.Is(err, repository.ErrEventNotFound) {
			writeJSON(w, http.StatusNotFound, map[string]string{"error": "not_found"})
			return
		}
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "internal_error"})
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (s *Server) handleConsumeOnce(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
		return
	}
	if s.gatewayConsumerService == nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "gateway_consumer_unavailable"})
		return
	}
	var payload struct {
		Consumer string `json:"consumer"`
		Cursor   string `json:"cursor"`
	}
	if r.Body != nil {
		if err := json.NewDecoder(r.Body).Decode(&payload); err != nil && err.Error() != "EOF" {
			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_json"})
			return
		}
	}
	out, err := s.gatewayConsumerService.ConsumeOnce(r.Context(), gatewayconsumer.ConsumeOnceInput{Consumer: payload.Consumer, Cursor: payload.Cursor})
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "consume_failed"})
		return
	}
	writeJSON(w, http.StatusOK, out)
}

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

// handleAdmissionRun runs admission test for a specific candidate
func (s *Server) handleAdmissionRun(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
		return
	}
	if s.admissionService == nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "admission_service_unavailable"})
		return
	}

	var payload struct {
		CandidateID string `json:"candidate_id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_json"})
		return
	}
	if strings.TrimSpace(payload.CandidateID) == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing_candidate_id"})
		return
	}

	result, err := s.admissionService.RunAdmission(r.Context(), payload.CandidateID)
	if err != nil {
		switch {
		case errors.Is(err, admission.ErrCandidateNotFound):
			writeJSON(w, http.StatusNotFound, map[string]string{"error": "candidate_not_found"})
		case errors.Is(err, admission.ErrCandidateNotRunnable):
			writeJSON(w, http.StatusConflict, map[string]string{"error": "candidate_not_runnable"})
		default:
			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "admission_run_failed"})
		}
		return
	}

	writeJSON(w, http.StatusOK, result)
}

// handleAdmissionCandidates lists candidates pending admission testing
func (s *Server) handleAdmissionCandidates(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method_not_allowed"})
		return
	}
	if s.admissionService == nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "admission_service_unavailable"})
		return
	}

	candidates := s.admissionService.GetRunnableCandidates(r.Context())
	writeJSON(w, http.StatusOK, map[string]any{"items": candidates})
}

func domainAccountStatus(raw string) domain.AccountStatus {
	return domain.AccountStatus(raw)
}