package main

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

	"github.com/pressly/goose/v3"
	_ "modernc.org/sqlite"
)

//go:embed migrations/*.sql
var embedMigrations embed.FS

type sqliteStore struct {
	db *sql.DB
}

func newSqliteStore(path string) (*sqliteStore, error) {
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, fmt.Errorf("open sqlite: %w", err)
	}

	db.SetMaxOpenConns(1)

	goose.SetBaseFS(embedMigrations)

	if err := goose.SetDialect("sqlite3"); err != nil {
		db.Close()
		return nil, fmt.Errorf("set dialect: %w", err)
	}

	if err := goose.Up(db, "migrations"); err != nil {
		db.Close()
		return nil, fmt.Errorf("migrate: %w", err)
	}

	return &sqliteStore{db: db}, nil
}

func (s *sqliteStore) save(ctx context.Context, note, host, user, context_ string, repos, tags []string, publicID int64) (int64, error) {
	reposJSON := marshalStringSlice(repos)
	tagsJSON := marshalStringSlice(tags)

	result, err := s.db.ExecContext(ctx,
		`INSERT INTO flashcard (public_id, version, note, repos, host, tags, "user", context)
		 VALUES (?, 1, ?, ?, ?, ?, ?, ?)`,
		publicID, note, reposJSON, host, tagsJSON, user, context_,
	)
	if err != nil {
		return 0, fmt.Errorf("insert: %w", err)
	}

	id, err := result.LastInsertId()
	if err != nil {
		return 0, fmt.Errorf("last insert id: %w", err)
	}

	if publicID == 0 {
		_, err = s.db.ExecContext(ctx, `UPDATE flashcard SET public_id = ? WHERE _id = ?`, id, id)
		if err != nil {
			return 0, fmt.Errorf("set public_id: %w", err)
		}
	}

	return id, nil
}

func (s *sqliteStore) getByID(ctx context.Context, id int64) (*entry, error) {
	row := s.db.QueryRowContext(ctx,
		`SELECT _id, public_id, version, note, repos, host, tags, "user", context, delete_timestamp, created
		 FROM flashcard WHERE _id = ?`, id,
	)

	var e entry
	var reposJSON, tagsJSON sql.NullString
	var host, user, context_, deleteTimestamp sql.NullString

	err := row.Scan(&e.ID, &e.PublicID, &e.Version, &e.Note, &reposJSON, &host, &tagsJSON, &user, &context_, &deleteTimestamp, &e.Created)
	if err == sql.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("query: %w", err)
	}

	if reposJSON.Valid {
		e.Repos = unmarshalStringSlice(reposJSON.String)
	}
	if tagsJSON.Valid {
		e.Tags = unmarshalStringSlice(tagsJSON.String)
	}
	if host.Valid {
		e.Host = host.String
	}
	if user.Valid {
		e.User = user.String
	}
	if context_.Valid {
		e.Context = context_.String
	}
	if deleteTimestamp.Valid {
		e.DeleteTimestamp = deleteTimestamp.String
	}

	return &e, nil
}

func (s *sqliteStore) getLatestByPublicID(ctx context.Context, publicID int64) (*entry, error) {
	row := s.db.QueryRowContext(ctx,
		`SELECT _id, public_id, version, note, repos, host, tags, "user", context, delete_timestamp, created
		 FROM flashcard WHERE public_id = ? ORDER BY version DESC LIMIT 1`, publicID,
	)

	var e entry
	var reposJSON, tagsJSON sql.NullString
	var host, user, context_, deleteTimestamp sql.NullString

	err := row.Scan(&e.ID, &e.PublicID, &e.Version, &e.Note, &reposJSON, &host, &tagsJSON, &user, &context_, &deleteTimestamp, &e.Created)
	if err == sql.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("query: %w", err)
	}

	if reposJSON.Valid {
		e.Repos = unmarshalStringSlice(reposJSON.String)
	}
	if tagsJSON.Valid {
		e.Tags = unmarshalStringSlice(tagsJSON.String)
	}
	if host.Valid {
		e.Host = host.String
	}
	if user.Valid {
		e.User = user.String
	}
	if context_.Valid {
		e.Context = context_.String
	}
	if deleteTimestamp.Valid {
		e.DeleteTimestamp = deleteTimestamp.String
	}

	return &e, nil
}

func (s *sqliteStore) tombstone(ctx context.Context, publicID int64, version int) (int64, error) {
	result, err := s.db.ExecContext(ctx,
		`INSERT INTO flashcard (public_id, version, note, delete_timestamp)
		 VALUES (?, ?, '', datetime('now'))`,
		publicID, version,
	)
	if err != nil {
		return 0, fmt.Errorf("tombstone: %w", err)
	}

	id, err := result.LastInsertId()
	if err != nil {
		return 0, fmt.Errorf("last insert id: %w", err)
	}

	return id, nil
}

func (s *sqliteStore) close() error {
	return s.db.Close()
}

func marshalStringSlice(ss []string) string {
	if len(ss) == 0 {
		return "[]"
	}
	b, _ := json.Marshal(ss)
	return string(b)
}

func unmarshalStringSlice(raw string) []string {
	if raw == "" || raw == "[]" || raw == "null" {
		return nil
	}
	var ss []string
	if err := json.Unmarshal([]byte(raw), &ss); err != nil {
		return nil
	}
	return ss
}

func parseStringSlice(raw any) []string {
	if raw == nil {
		return nil
	}
	arr, ok := raw.([]any)
	if !ok {
		return nil
	}
	result := make([]string, 0, len(arr))
	for _, v := range arr {
		if s, ok := v.(string); ok {
			result = append(result, s)
		}
	}
	return result
}

func parseOptionalString(raw any) string {
	if s, ok := raw.(string); ok && strings.TrimSpace(s) != "" {
		return s
	}
	return ""
}

func parseInt64(raw any) int64 {
	if raw == nil {
		return 0
	}
	switch v := raw.(type) {
	case float64:
		return int64(v)
	case int64:
		return v
	case int:
		return int64(v)
	}
	return 0
}