package httpapi

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"sync"
	"time"

	"ai-service/internal/config"
	"ai-service/internal/model"
	"ai-service/internal/store"

	"github.com/google/uuid"
)

type Server struct {
	store       *store.Store
	cfg         config.Config
	providerMu  sync.Mutex
	providerOKs map[string]providerHealthSnapshot
}

func NewServer(store *store.Store, cfg config.Config) http.Handler {
	return &Server{store: store, cfg: cfg, providerOKs: make(map[string]providerHealthSnapshot)}
}

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	path := strings.TrimSuffix(r.URL.Path, "/")
	if path == "" {
		path = "/"
	}
	if !s.requireAPIToken(path, r) {
		writeError(w, http.StatusUnauthorized, "unauthorized")
		return
	}
	switch {
	case r.Method == http.MethodGet && path == "/healthz":
		writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
	case r.Method == http.MethodGet && path == "/readyz":
		s.handleReady(w, r)
	case r.Method == http.MethodGet && path == "/health/detail":
		s.handleHealthDetail(w, r)
	case r.Method == http.MethodGet && path == "/":
		writeJSON(w, http.StatusOK, map[string]string{"service": "ai-service"})
	case r.Method == http.MethodPost && path == "/api/v1/jobs":
		s.handleCreateJob(w, r)
	case r.Method == http.MethodGet && path == "/api/v1/jobs":
		s.handleListJobs(w, r)
	case r.Method == http.MethodPost && path == "/api/v1/jobs/batch":
		s.handleCreateBatch(w, r)
	case r.Method == http.MethodPost && path == "/api/v1/jobs/retry":
		s.handleRetryJobs(w, r)
	case r.Method == http.MethodPost && path == "/api/v1/jobs/cancel":
		s.handleCancelJobs(w, r)
	case r.Method == http.MethodPost && path == "/api/v1/jobs/claim":
		s.handleClaimJobs(w, r)
	case r.Method == http.MethodGet && strings.HasPrefix(path, "/api/v1/jobs/"):
		s.handleGetJob(w, r, path)
	case r.Method == http.MethodPost && strings.HasPrefix(path, "/api/v1/jobs/") && strings.HasSuffix(path, "/retry"):
		s.handleRetryJob(w, r, path)
	case r.Method == http.MethodPost && strings.HasPrefix(path, "/api/v1/jobs/") && strings.HasSuffix(path, "/cancel"):
		s.handleCancelJob(w, r, path)
	case r.Method == http.MethodPost && strings.HasPrefix(path, "/api/v1/jobs/") && strings.HasSuffix(path, "/complete"):
		s.handleCompleteJob(w, r, path)
	case r.Method == http.MethodPost && strings.HasPrefix(path, "/api/v1/jobs/") && strings.HasSuffix(path, "/fail"):
		s.handleFailJob(w, r, path)
	case r.Method == http.MethodGet && path == "/api/v1/stats":
		s.handleStats(w, r)
	case r.Method == http.MethodGet && path == "/api/v1/providers/status":
		s.handleProviderStatus(w, r)
	case r.Method == http.MethodGet && path == "/api/v1/infra/status":
		s.handleInfraStatus(w, r)
	case r.Method == http.MethodGet && path == "/api/v1/dashboard":
		s.handleDashboard(w, r)
	default:
		writeError(w, http.StatusNotFound, "not found")
	}
}

func (s *Server) handleReady(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := contextWithTimeout(r, 3*time.Second)
	defer cancel()
	if err := s.store.Ping(ctx); err != nil {
		writeError(w, http.StatusServiceUnavailable, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "ready"})
}

func (s *Server) handleCreateJob(w http.ResponseWriter, r *http.Request) {
	var req model.CreateJob
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "bad json")
		return
	}
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	job, err := s.store.CreateJob(ctx, req)
	if err != nil {
		status := http.StatusInternalServerError
		if isValidationError(err) {
			status = http.StatusBadRequest
		}
		writeError(w, status, err.Error())
		return
	}
	writeJSON(w, http.StatusCreated, job)
}

type listJobsResponse struct {
	Jobs []*model.Job `json:"jobs"`
}

func (s *Server) handleListJobs(w http.ResponseWriter, r *http.Request) {
	filter := jobFilterFromQuery(r)
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	jobs, err := s.store.ListJobs(ctx, filter)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, listJobsResponse{Jobs: jobs})
}

type createBatchRequest struct {
	OwnerService string            `json:"owner_service"`
	TaskType     string            `json:"task_type"`
	ModelProfile string            `json:"model_profile"`
	Priority     int               `json:"priority"`
	MaxAttempts  int               `json:"max_attempts"`
	Jobs         []model.CreateJob `json:"jobs"`
}

type createBatchResponse struct {
	Jobs []*model.Job `json:"jobs"`
}

const maxCreateBatchJobs = 1000

func (s *Server) handleCreateBatch(w http.ResponseWriter, r *http.Request) {
	var req createBatchRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "bad json")
		return
	}
	if len(req.Jobs) == 0 {
		writeError(w, http.StatusBadRequest, "jobs is required")
		return
	}
	if len(req.Jobs) > maxCreateBatchJobs {
		writeError(w, http.StatusBadRequest, fmt.Sprintf("jobs limit is %d", maxCreateBatchJobs))
		return
	}
	ctx, cancel := contextWithTimeout(r, 20*time.Second)
	defer cancel()
	items := make([]model.CreateJob, 0, len(req.Jobs))
	for _, item := range req.Jobs {
		if strings.TrimSpace(item.OwnerService) == "" {
			item.OwnerService = req.OwnerService
		}
		if strings.TrimSpace(item.TaskType) == "" {
			item.TaskType = req.TaskType
		}
		if strings.TrimSpace(item.ModelProfile) == "" {
			item.ModelProfile = req.ModelProfile
		}
		if item.Priority == 0 {
			item.Priority = req.Priority
		}
		if item.MaxAttempts == 0 {
			item.MaxAttempts = req.MaxAttempts
		}
		items = append(items, item)
	}
	jobs, err := s.store.CreateJobs(ctx, items)
	if err != nil {
		status := http.StatusInternalServerError
		if isValidationError(err) {
			status = http.StatusBadRequest
		}
		writeError(w, status, err.Error())
		return
	}
	writeJSON(w, http.StatusCreated, createBatchResponse{Jobs: jobs})
}

func (s *Server) handleRetryJobs(w http.ResponseWriter, r *http.Request) {
	var req model.JobFilter
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "bad json")
		return
	}
	if !hasAnyFilter(req) {
		writeError(w, http.StatusBadRequest, "at least one filter is required")
		return
	}
	ctx, cancel := contextWithTimeout(r, 20*time.Second)
	defer cancel()
	updated, err := s.store.RetryJobs(ctx, req)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, model.BatchActionResult{Updated: updated})
}

func (s *Server) handleCancelJobs(w http.ResponseWriter, r *http.Request) {
	var req model.JobFilter
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "bad json")
		return
	}
	if !hasAnyFilter(req) {
		writeError(w, http.StatusBadRequest, "at least one filter is required")
		return
	}
	ctx, cancel := contextWithTimeout(r, 20*time.Second)
	defer cancel()
	updated, err := s.store.CancelJobs(ctx, req)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, model.BatchActionResult{Updated: updated})
}

type claimJobsResponse struct {
	Jobs []*model.Job `json:"jobs"`
}

func (s *Server) handleClaimJobs(w http.ResponseWriter, r *http.Request) {
	var req model.ClaimJobs
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "bad json")
		return
	}
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	jobs, err := s.store.ClaimJobs(ctx, req)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, claimJobsResponse{Jobs: jobs})
}

func (s *Server) handleGetJob(w http.ResponseWriter, r *http.Request, path string) {
	id, err := jobIDFromPath(path, false)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	job, err := s.store.GetJob(ctx, id)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if job == nil {
		writeError(w, http.StatusNotFound, "job not found")
		return
	}
	writeJSON(w, http.StatusOK, job)
}

func (s *Server) handleRetryJob(w http.ResponseWriter, r *http.Request, path string) {
	id, err := jobIDFromActionPath(path, "retry")
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	job, err := s.store.RetryJob(ctx, id)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if job == nil {
		writeError(w, http.StatusNotFound, "retryable job not found")
		return
	}
	writeJSON(w, http.StatusOK, job)
}

func (s *Server) handleCancelJob(w http.ResponseWriter, r *http.Request, path string) {
	id, err := jobIDFromActionPath(path, "cancel")
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	job, err := s.store.CancelJob(ctx, id)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if job == nil {
		writeError(w, http.StatusNotFound, "cancellable job not found")
		return
	}
	writeJSON(w, http.StatusOK, job)
}

func (s *Server) handleCompleteJob(w http.ResponseWriter, r *http.Request, path string) {
	id, err := jobIDFromActionPath(path, "complete")
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	var req model.CompleteJob
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "bad json")
		return
	}
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	job, err := s.store.CompleteJob(ctx, id, req)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if job == nil {
		writeError(w, http.StatusNotFound, "running job not found")
		return
	}
	writeJSON(w, http.StatusOK, job)
}

func (s *Server) handleFailJob(w http.ResponseWriter, r *http.Request, path string) {
	id, err := jobIDFromActionPath(path, "fail")
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	var req model.FailJob
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "bad json")
		return
	}
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	job, err := s.store.FailJob(ctx, id, req)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if job == nil {
		writeError(w, http.StatusNotFound, "running job not found")
		return
	}
	writeJSON(w, http.StatusOK, job)
}

func (s *Server) handleStats(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()
	stats, err := s.store.Stats(ctx, s.cfg.WorkerLeaseTimeout)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, stats)
}

func jobIDFromPath(path string, retry bool) (uuid.UUID, error) {
	raw := strings.TrimPrefix(path, "/api/v1/jobs/")
	if retry {
		raw = strings.TrimSuffix(raw, "/retry")
	}
	id, err := uuid.Parse(strings.Trim(raw, "/"))
	if err != nil {
		return uuid.Nil, errors.New("bad job id")
	}
	return id, nil
}

func jobIDFromActionPath(path string, action string) (uuid.UUID, error) {
	raw := strings.TrimPrefix(path, "/api/v1/jobs/")
	raw = strings.TrimSuffix(raw, "/"+action)
	id, err := uuid.Parse(strings.Trim(raw, "/"))
	if err != nil {
		return uuid.Nil, errors.New("bad job id")
	}
	return id, nil
}

func isValidationError(err error) bool {
	msg := err.Error()
	return strings.Contains(msg, " is required")
}

func jobFilterFromQuery(r *http.Request) model.JobFilter {
	q := r.URL.Query()
	return model.JobFilter{
		OwnerService: q.Get("owner_service"),
		OwnerRef:     q.Get("owner_ref"),
		TaskType:     q.Get("task_type"),
		ModelProfile: q.Get("model_profile"),
		Statuses:     splitCSV(q.Get("status")),
		ErrorCodes:   splitCSV(q.Get("error_code")),
		Limit:        parseIntDefault(q.Get("limit"), 100),
		Offset:       parseIntDefault(q.Get("offset"), 0),
	}
}

func splitCSV(raw string) []string {
	if strings.TrimSpace(raw) == "" {
		return nil
	}
	parts := strings.Split(raw, ",")
	out := make([]string, 0, len(parts))
	for _, part := range parts {
		if v := strings.TrimSpace(part); v != "" {
			out = append(out, v)
		}
	}
	return out
}

func parseIntDefault(raw string, fallback int) int {
	if strings.TrimSpace(raw) == "" {
		return fallback
	}
	var out int
	if _, err := fmt.Sscanf(raw, "%d", &out); err != nil {
		return fallback
	}
	return out
}

func hasAnyFilter(filter model.JobFilter) bool {
	return strings.TrimSpace(filter.OwnerService) != "" ||
		strings.TrimSpace(filter.OwnerRef) != "" ||
		strings.TrimSpace(filter.TaskType) != "" ||
		strings.TrimSpace(filter.ModelProfile) != "" ||
		len(filter.Statuses) > 0 ||
		len(filter.ErrorCodes) > 0
}