package dbi

import (
	"context"
	"database/sql"
	"reflect"
	"strings"

	"atlas9.dev/c/core"
)

func Get(ctx context.Context, db DBI, val any, query string, vals ...any) error {

	rows, err := db.Query(ctx, query, vals...)
	if err != nil {
		return err
	}
	defer rows.Close()

	if !rows.Next() {
		if err := rows.Err(); err != nil {
			return err
		}
		return core.ErrNotFound
	}

	cols, err := rows.Columns()
	if err != nil {
		return err
	}

	rv := reflect.ValueOf(val).Elem()
	rt := rv.Type()

	if _, ok := val.(sql.Scanner); ok {
		err = rows.Scan(val)
	} else if rt.Kind() == reflect.Struct {
		// Build a map of lowercase field name -> field index.
		// Column names are matched by lowercasing and stripping underscores,
		// so SQL snake_case columns map to Go PascalCase fields naturally:
		//   picture_url -> pictureurl -> PictureURL
		//   user_id     -> userid     -> UserID
		fieldMap := make(map[string]int, rt.NumField())
		for i := 0; i < rt.NumField(); i++ {
			f := rt.Field(i)
			if f.IsExported() {
				fieldMap[strings.ToLower(f.Name)] = i
			}
		}

		dest := make([]any, len(cols))
		for i, col := range cols {
			if fi, ok := fieldMap[strings.ReplaceAll(col, "_", "")]; ok {
				dest[i] = rv.Field(fi).Addr().Interface()
			} else {
				dest[i] = new(any)
			}
		}
		err = rows.Scan(dest...)
	} else {
		err = rows.Scan(val)
	}

	if err != nil {
		return err
	}
	return nil
}