package db

import (
	"context"
	"fmt"
	"sort"
	"strings"
)

func (c *Client) Update(
	ctx context.Context,
	table string,
	keyField string,
	data map[string]any,
) error {
	keyVal, err := validateData(table, keyField, data)
	if err != nil {
		return err
	}

	var (
		setClauses []string
		args       []any
		i          = 1
	)

	for col, val := range data {
		if col == keyField {
			continue
		}
		setClauses = append(setClauses, fmt.Sprintf("%s=$%d", col, i))
		args = append(args, val)
		i++
	}

	// WHERE 条件
	where := fmt.Sprintf("%s=$%d", keyField, i)
	args = append(args, keyVal)

	sql := fmt.Sprintf(
		"UPDATE %s SET %s WHERE %s",
		table,
		strings.Join(setClauses, ", "),
		where,
	)

	_, err = c.exec().Exec(ctx, sql, args...)
	return err
}

func (c *Client) BatchUpdate(
	ctx context.Context,
	table string,
	keyField string,
	dataList []map[string]any,
) error {

	if len(dataList) == 0 {
		return fmt.Errorf("数据不能为空")
	}

	// 用第一条数据确定字段
	first := dataList[0]
	if _, err := validateData(table, keyField, first); err != nil {
		return err
	}

	// 提取字段（排除主键）+ 排序（关键）
	var columns []string
	for col := range first {
		if col != keyField {
			columns = append(columns, col)
		}
	}
	sort.Strings(columns)

	var (
		args     []any
		argIndex = 1
	)

	// CASE 语句
	var setClauses []string

	for _, col := range columns {
		var caseBuilder strings.Builder

		caseBuilder.WriteString(fmt.Sprintf("%s = CASE %s ", col, keyField))

		for _, data := range dataList {
			// 校验 key
			keyVal, err := validateData(table, keyField, data)
			if err != nil {
				return err
			}

			val, ok := data[col]
			if !ok {
				return fmt.Errorf("缺少字段: %s", col)
			}

			caseBuilder.WriteString(fmt.Sprintf(
				"WHEN $%d THEN $%d ",
				argIndex,
				argIndex+1,
			))

			args = append(args, keyVal, val)
			argIndex += 2
		}

		caseBuilder.WriteString("END")
		setClauses = append(setClauses, caseBuilder.String())
	}

	// WHERE IN
	var wherePlaceholders []string

	for _, data := range dataList {
		keyVal, ok := data[keyField]
		if !ok || keyVal == nil {
			return fmt.Errorf("缺少主键字段值: %s", keyField)
		}

		wherePlaceholders = append(wherePlaceholders, fmt.Sprintf("$%d", argIndex))
		args = append(args, keyVal)
		argIndex++
	}

	sql := fmt.Sprintf(
		"UPDATE %s SET %s WHERE %s IN (%s)",
		table,
		strings.Join(setClauses, ", "),
		keyField,
		strings.Join(wherePlaceholders, ", "),
	)

	_, err := c.exec().Exec(ctx, sql, args...)
	return err
}