package store

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"

	"github.com/wotra/wotra/internal/domain"
)

// SyncStore manages the sync_log and server_version.
type SyncStore struct {
	db *sql.DB
}

func NewSyncStore(db *sql.DB) *SyncStore {
	return &SyncStore{db: db}
}

type SyncChange struct {
	Entity   string `json:"entity"`
	EntityID string `json:"entity_id"`
	Op       string `json:"op"` // "upsert" | "delete"
	Version  int64  `json:"version"`
	Payload  string `json:"payload"`
}

// Pull returns all sync_log rows with version > sinceVersion.
func (s *SyncStore) Pull(ctx context.Context, sinceVersion int64) ([]SyncChange, int64, error) {
	rows, err := s.db.QueryContext(ctx,
		`SELECT entity, entity_id, op, version, payload FROM sync_log
		 WHERE version > ? ORDER BY version ASC`, sinceVersion)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()
	var changes []SyncChange
	var maxVersion int64 = sinceVersion
	for rows.Next() {
		var c SyncChange
		if err := rows.Scan(&c.Entity, &c.EntityID, &c.Op, &c.Version, &c.Payload); err != nil {
			return nil, 0, err
		}
		if c.Version > maxVersion {
			maxVersion = c.Version
		}
		changes = append(changes, c)
	}
	return changes, maxVersion, rows.Err()
}

// nextVersion returns the next monotonic version number.
func (s *SyncStore) nextVersion(ctx context.Context) (int64, error) {
	var max sql.NullInt64
	err := s.db.QueryRowContext(ctx, `SELECT MAX(version) FROM sync_log`).Scan(&max)
	if err != nil {
		return 0, err
	}
	if !max.Valid {
		return 1, nil
	}
	return max.Int64 + 1, nil
}

// LogEntry appends an entry upsert to the sync log.
func (s *SyncStore) LogEntry(ctx context.Context, e *domain.Entry) error {
	payload, err := json.Marshal(e)
	if err != nil {
		return err
	}
	return s.log(ctx, "entries", e.ID, "upsert", string(payload))
}

// LogEntryDelete appends an entry delete to the sync log.
func (s *SyncStore) LogEntryDelete(ctx context.Context, id string) error {
	payload := fmt.Sprintf(`{"id":%q}`, id)
	return s.log(ctx, "entries", id, "delete", payload)
}

// LogClosedDay appends a closed_day upsert to the sync log.
func (s *SyncStore) LogClosedDay(ctx context.Context, d *domain.ClosedDay) error {
	payload, err := json.Marshal(d)
	if err != nil {
		return err
	}
	return s.log(ctx, "closed_days", d.DayKey, "upsert", string(payload))
}

// LogClosedWeek appends a closed_week upsert to the sync log.
func (s *SyncStore) LogClosedWeek(ctx context.Context, w *domain.ClosedWeek) error {
	payload, err := json.Marshal(w)
	if err != nil {
		return err
	}
	return s.log(ctx, "closed_weeks", w.WeekKey, "upsert", string(payload))
}

func (s *SyncStore) log(ctx context.Context, entity, entityID, op, payload string) error {
	version, err := s.nextVersion(ctx)
	if err != nil {
		return err
	}
	_, err = s.db.ExecContext(ctx,
		`INSERT INTO sync_log (entity, entity_id, op, version, payload) VALUES (?, ?, ?, ?, ?)`,
		entity, entityID, op, version, payload)
	return err
}