// Package search queries the FTS5 index over media item titles and paths.
package search

import (
	"context"
	"database/sql"
	"fmt"
	"strings"
)

// Result is one matching item.
type Result struct {
	ID        int64  `json:"id"`
	LibraryID int64  `json:"library_id"`
	Kind      string `json:"kind"`
	Path      string `json:"path"`
	Title     string `json:"title"`
}

// Query searches visible libraries for a free-text string.
//
// Each whitespace-separated term becomes a quoted FTS5 token joined by
// implicit AND. Quoting is not cosmetic: raw user input containing a quote, a
// hyphen, or the word OR would otherwise be parsed as FTS5 query syntax and
// raise an error, or silently change the meaning of the search.
func Query(ctx context.Context, db *sql.DB, q string, libraryIDs []int64, limit int) ([]Result, error) {
	terms := ftsTerms(q)
	if len(terms) == 0 {
		return []Result{}, nil
	}
	if len(libraryIDs) == 0 {
		return []Result{}, nil
	}
	if limit <= 0 || limit > 200 {
		limit = 50
	}

	placeholders := make([]string, len(libraryIDs))
	args := make([]any, 0, len(libraryIDs)+2)
	args = append(args, strings.Join(terms, " "))
	for i, id := range libraryIDs {
		placeholders[i] = "?"
		args = append(args, id)
	}
	args = append(args, limit)

	query := `
		SELECT i.id, i.library_id, i.kind, i.path, i.title
		FROM media_search s
		JOIN media_items i ON i.id = s.rowid
		WHERE media_search MATCH ?
		  AND i.missing = 0
		  AND i.library_id IN (` + strings.Join(placeholders, ",") + `)
		ORDER BY bm25(media_search)
		LIMIT ?`

	rows, err := db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("search: query: %w", err)
	}
	defer rows.Close()

	out := []Result{}
	for rows.Next() {
		var r Result
		if err := rows.Scan(&r.ID, &r.LibraryID, &r.Kind, &r.Path, &r.Title); err != nil {
			return nil, err
		}
		out = append(out, r)
	}
	return out, rows.Err()
}

// ftsTerms turns free text into a safe FTS5 expression: every term quoted, so
// the result is always valid FTS5 and always means "all these words".
func ftsTerms(q string) []string {
	var terms []string
	for _, field := range strings.Fields(q) {
		// A double quote inside a quoted FTS5 string is escaped by doubling it.
		escaped := strings.ReplaceAll(field, `"`, `""`)
		terms = append(terms, `"`+escaped+`"`)
	}
	return terms
}