package api

import (
	"database/sql"
	"encoding/json"
	"log/slog"
	"net/http"
	"strconv"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/syncserver/internal/models"
	"github.com/syncserver/internal/scheduler"
)

type ScheduleHandler struct {
	db *sql.DB
}

func NewScheduleHandler(db *sql.DB) *ScheduleHandler {
	return &ScheduleHandler{db: db}
}

func (h *ScheduleHandler) List(w http.ResponseWriter, r *http.Request) {
	repo := models.NewScheduleRepository(h.db)
	schedules, err := repo.GetAll()
	if err != nil {
		slog.Error("failed to fetch schedules", "error", err)
		writeError(w, http.StatusInternalServerError, "failed to fetch schedules")
		return
	}

	pairRepo := models.NewSyncPairRepository(h.db)
	pairs, err := pairRepo.GetAll()
	if err != nil {
		slog.Error("failed to fetch sync pairs", "error", err)
		writeError(w, http.StatusInternalServerError, "failed to fetch sync pairs")
		return
	}
	pairMap := make(map[int64]string)
	for _, p := range pairs {
		pairMap[p.ID] = p.Name
	}

	out := make([]ScheduleResponse, len(schedules))
	for i, s := range schedules {
		out[i] = scheduleToResp(s, pairMap)
	}
	writeJSON(w, out)
}

func (h *ScheduleHandler) Get(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	repo := models.NewScheduleRepository(h.db)
	s, err := repo.GetByID(id)
	if err == sql.ErrNoRows {
		writeError(w, http.StatusNotFound, "schedule not found")
		return
	}
	if err != nil {
		slog.Error("failed to fetch schedule", "id", id, "error", err)
		writeError(w, http.StatusInternalServerError, "failed to fetch schedule")
		return
	}

	pairRepo := models.NewSyncPairRepository(h.db)
	pairs, err := pairRepo.GetAll()
	if err != nil {
		slog.Error("failed to fetch sync pairs", "error", err)
		writeError(w, http.StatusInternalServerError, "failed to fetch sync pairs")
		return
	}
	pairMap := make(map[int64]string)
	for _, p := range pairs {
		pairMap[p.ID] = p.Name
	}

	writeJSON(w, scheduleToResp(*s, pairMap))
}

func (h *ScheduleHandler) Create(w http.ResponseWriter, r *http.Request) {
	var req CreateScheduleRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.SyncPairID <= 0 {
		writeError(w, http.StatusBadRequest, "sync_pair_id is required")
		return
	}
	if req.CronExpr == "" {
		writeError(w, http.StatusBadRequest, "cron_expr is required")
		return
	}

	_, err := scheduler.ParseCron(req.CronExpr)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid cron expression: "+err.Error())
		return
	}

	pairRepo := models.NewSyncPairRepository(h.db)
	_, err = pairRepo.GetByID(req.SyncPairID)
	if err == sql.ErrNoRows {
		writeError(w, http.StatusBadRequest, "sync_pair not found")
		return
	}
	if err != nil {
		slog.Error("failed to fetch sync pair", "id", req.SyncPairID, "error", err)
		writeError(w, http.StatusInternalServerError, "failed to validate sync pair")
		return
	}

	expr, _ := scheduler.ParseCron(req.CronExpr)
	var nextRun *time.Time
	if expr != nil {
		t := scheduler.NextRun(expr, time.Now().UTC())
		nextRun = &t
	}

	s := &models.Schedule{
		SyncPairID: req.SyncPairID,
		CronExpr:   req.CronExpr,
		NextRunAt:  nextRun,
		Enabled:    req.Enabled,
	}

	repo := models.NewScheduleRepository(h.db)
	id, err := repo.Create(s)
	if err != nil {
		slog.Error("failed to create schedule", "error", err)
		writeError(w, http.StatusInternalServerError, "failed to create schedule")
		return
	}
	s.ID = id

	pairs, _ := pairRepo.GetAll()
	pairMap := make(map[int64]string)
	for _, p := range pairs {
		pairMap[p.ID] = p.Name
	}

	w.Header().Set("Location", "/api/schedules/"+strconv.FormatInt(id, 10))
	writeJSON(w, scheduleToResp(*s, pairMap), http.StatusCreated)
}

func (h *ScheduleHandler) Update(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}

	var req UpdateScheduleRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	repo := models.NewScheduleRepository(h.db)
	existing, err := repo.GetByID(id)
	if err == sql.ErrNoRows {
		writeError(w, http.StatusNotFound, "schedule not found")
		return
	}
	if err != nil {
		slog.Error("failed to fetch schedule", "id", id, "error", err)
		writeError(w, http.StatusInternalServerError, "failed to fetch schedule")
		return
	}

	if req.CronExpr != "" {
		_, err := scheduler.ParseCron(req.CronExpr)
		if err != nil {
			writeError(w, http.StatusBadRequest, "invalid cron expression: "+err.Error())
			return
		}
		existing.CronExpr = req.CronExpr
		expr, _ := scheduler.ParseCron(req.CronExpr)
		if expr != nil {
			t := scheduler.NextRun(expr, time.Now().UTC())
			existing.NextRunAt = &t
		}
	}

	if req.Enabled {
		existing.Enabled = true
	} else if req.Enabled == false {
		existing.Enabled = false
	}

	if err := repo.Update(existing); err != nil {
		slog.Error("failed to update schedule", "id", id, "error", err)
		writeError(w, http.StatusInternalServerError, "failed to update schedule")
		return
	}

	pairRepo := models.NewSyncPairRepository(h.db)
	pairs, _ := pairRepo.GetAll()
	pairMap := make(map[int64]string)
	for _, p := range pairs {
		pairMap[p.ID] = p.Name
	}

	writeJSON(w, scheduleToResp(*existing, pairMap))
}

func (h *ScheduleHandler) Delete(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}

	repo := models.NewScheduleRepository(h.db)
	if err := repo.Delete(id); err != nil {
		slog.Error("failed to delete schedule", "id", id, "error", err)
		writeError(w, http.StatusInternalServerError, "failed to delete schedule")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func scheduleToResp(s models.Schedule, pairMap map[int64]string) ScheduleResponse {
	resp := ScheduleResponse{
		ID:          s.ID,
		SyncPairID:  s.SyncPairID,
		SyncPairName: pairMap[s.SyncPairID],
		CronExpr:    s.CronExpr,
		Enabled:     s.Enabled,
		CreatedAt:  s.CreatedAt.Format(time.RFC3339),
	}
	if s.NextRunAt != nil {
		t := s.NextRunAt.Format(time.RFC3339)
		resp.NextRun = &t
	}
	return resp
}