package storage

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

// UploadMeta is the database index record for an uploaded file.
//
// The .meta.json sidecar remains the source of truth; this struct is the
// queryable mirror used by the admin UI.
type UploadMeta struct {
	FileID     string    `json:"file_id"`
	Name       string    `json:"name"`
	Size       int64     `json:"size"`
	SHA256     string    `json:"sha256"`
	UploadedAt time.Time `json:"uploaded_at"`
}

// UploadRepo provides CRUD operations for upload file index records.
type UploadRepo struct {
	db *DB
}

// Uploads returns a repository bound to this DB handle.
func (d *DB) Uploads() *UploadRepo {
	return &UploadRepo{db: d}
}

// Create inserts a new upload index record. Timestamps are stored as Unix
// nanoseconds for stable ORDER BY semantics.
func (r *UploadRepo) Create(ctx context.Context, fileID, name string, size int64, sha256Hex string, uploadedAt time.Time) error {
	_, err := r.db.sqlDB.ExecContext(ctx, `
		INSERT INTO upload_files (file_id, name, size, sha256, uploaded_at)
		VALUES (?, ?, ?, ?, ?)`,
		fileID, name, size, sha256Hex, uploadedAt.UnixNano(),
	)
	if err != nil {
		if strings.Contains(err.Error(), "UNIQUE constraint failed") {
			return fmt.Errorf("storage: create upload %s: primary key conflict: %w", fileID, err)
		}
		return fmt.Errorf("storage: create upload %s: %w", fileID, err)
	}
	return nil
}

// Get retrieves an upload index record by file_id. If the record does not
// exist, it returns ErrNotFound.
func (r *UploadRepo) Get(ctx context.Context, fileID string) (UploadMeta, error) {
	row := r.db.sqlDB.QueryRowContext(ctx, `
		SELECT file_id, name, size, sha256, uploaded_at
		FROM upload_files
		WHERE file_id = ?`, fileID)

	m, err := scanUpload(row.Scan)
	if errors.Is(err, sql.ErrNoRows) {
		return UploadMeta{}, ErrNotFound
	}
	if err != nil {
		return UploadMeta{}, fmt.Errorf("storage: get upload %s: %w", fileID, err)
	}
	return m, nil
}

// List returns upload index records ordered by uploaded_at descending.
//
// If search is non-empty, name is filtered with a case-insensitive LIKE.
// A limit of zero or less falls back to 100; values above 500 are capped.
func (r *UploadRepo) List(ctx context.Context, search string, limit int) ([]UploadMeta, error) {
	if limit <= 0 {
		limit = 100
	}
	if limit > 500 {
		limit = 500
	}

	var rows *sql.Rows
	var err error
	if search != "" {
		rows, err = r.db.sqlDB.QueryContext(ctx, `
			SELECT file_id, name, size, sha256, uploaded_at
			FROM upload_files
			WHERE name LIKE ?
			ORDER BY uploaded_at DESC
			LIMIT ?`,
			"%"+search+"%", limit,
		)
	} else {
		rows, err = r.db.sqlDB.QueryContext(ctx, `
			SELECT file_id, name, size, sha256, uploaded_at
			FROM upload_files
			ORDER BY uploaded_at DESC
			LIMIT ?`, limit)
	}
	if err != nil {
		return nil, fmt.Errorf("storage: list uploads: %w", err)
	}
	defer rows.Close()

	var out []UploadMeta
	for rows.Next() {
		m, err := scanUpload(rows.Scan)
		if err != nil {
			return nil, fmt.Errorf("storage: list uploads: %w", err)
		}
		out = append(out, m)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("storage: list uploads: %w", err)
	}
	if out == nil {
		// Force empty slice (not null) in JSON.
		out = []UploadMeta{}
	}
	return out, nil
}

// Delete removes an upload index record by file_id. If the record does not
// exist, it returns ErrNotFound.
func (r *UploadRepo) Delete(ctx context.Context, fileID string) error {
	res, err := r.db.sqlDB.ExecContext(ctx, `DELETE FROM upload_files WHERE file_id = ?`, fileID)
	if err != nil {
		return fmt.Errorf("storage: delete upload %s: %w", fileID, err)
	}
	n, err := res.RowsAffected()
	if err != nil {
		return fmt.Errorf("storage: delete upload %s: rows affected: %w", fileID, err)
	}
	if n == 0 {
		return ErrNotFound
	}
	return nil
}

func scanUpload(scan scanFunc) (UploadMeta, error) {
	var m UploadMeta
	var uploadedAt int64
	if err := scan(&m.FileID, &m.Name, &m.Size, &m.SHA256, &uploadedAt); err != nil {
		return UploadMeta{}, err
	}
	m.UploadedAt = time.Unix(0, uploadedAt)
	return m, nil
}