package db

import (
	"fmt"
	"sort"
	"strings"
	"time"

	"GoNavi-Wails/internal/connection"
)

// GenerateChangePreview 将 ChangeSet 转为可读 SQL 语句（不执行）。
// quoteIdent 用于引用列名/表名（MySQL: backtick, PostgreSQL: double quote）。
func GenerateChangePreview(tableName string, changes connection.ChangeSet, quoteIdent func(string) string) (deletes, updates, inserts []string) {
	qt := quoteIdent

	// Deletes
	for _, pk := range changes.Deletes {
		var conds []string
		for _, k := range sortedKeys(pk) {
			v := pk[k]
			conds = append(conds, fmt.Sprintf("%s = %s", qt(k), formatLiteral(v)))
		}
		if len(conds) > 0 {
			deletes = append(deletes, fmt.Sprintf("DELETE FROM %s WHERE %s;", qt(tableName), strings.Join(conds, " AND ")))
		}
	}

	// Updates
	for _, row := range changes.Updates {
		var sets []string
		for _, k := range sortedKeys(row.Values) {
			v := row.Values[k]
			sets = append(sets, fmt.Sprintf("%s = %s", qt(k), formatLiteral(v)))
		}
		if len(sets) == 0 {
			continue
		}
		var conds []string
		for _, k := range sortedKeys(row.Keys) {
			v := row.Keys[k]
			conds = append(conds, fmt.Sprintf("%s = %s", qt(k), formatLiteral(v)))
		}
		if len(conds) == 0 {
			continue
		}
		updates = append(updates, fmt.Sprintf("UPDATE %s SET %s WHERE %s;", qt(tableName), strings.Join(sets, ", "), strings.Join(conds, " AND ")))
	}

	// Inserts
	for _, row := range changes.Inserts {
		var cols []string
		var vals []string
		for _, k := range sortedKeys(row) {
			v := row[k]
			if v == nil {
				continue
			}
			cols = append(cols, qt(k))
			vals = append(vals, formatLiteral(v))
		}
		if len(cols) == 0 {
			continue
		}
		inserts = append(inserts, fmt.Sprintf("INSERT INTO %s (%s) VALUES (%s);", qt(tableName), strings.Join(cols, ", "), strings.Join(vals, ", ")))
	}

	return deletes, updates, inserts
}

// sortedKeys 返回 map 的键排序切片，保证输出确定性。
func sortedKeys(m map[string]interface{}) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}

// formatLiteral 将 Go 值转为 SQL 字面量字符串。
func formatLiteral(v interface{}) string {
	if v == nil {
		return "NULL"
	}
	switch t := v.(type) {
	case string:
		escaped := strings.ReplaceAll(t, "\\", "\\\\")
		escaped = strings.ReplaceAll(escaped, "'", "\\'")
		return fmt.Sprintf("'%s'", escaped)
	case float64:
		return formatNumber(t)
	case float32:
		return formatNumber(float64(t))
	case int:
		return fmt.Sprintf("%d", t)
	case int64:
		return fmt.Sprintf("%d", t)
	case int32:
		return fmt.Sprintf("%d", t)
	case int16:
		return fmt.Sprintf("%d", t)
	case int8:
		return fmt.Sprintf("%d", t)
	case uint64:
		return fmt.Sprintf("%d", t)
	case uint32:
		return fmt.Sprintf("%d", t)
	case uint16:
		return fmt.Sprintf("%d", t)
	case uint8:
		return fmt.Sprintf("%d", t)
	case uint:
		return fmt.Sprintf("%d", t)
	case time.Time:
		return fmt.Sprintf("'%s'", t.Format("2006-01-02 15:04:05"))
	case bool:
		if t {
			return "TRUE"
		}
		return "FALSE"
	case []byte:
		return formatLiteral(string(t))
	default:
		escaped := strings.ReplaceAll(fmt.Sprintf("%v", t), "'", "\\'")
		return fmt.Sprintf("'%s'", escaped)
	}
}

func formatNumber(f float64) string {
	if f == float64(int64(f)) {
		return fmt.Sprintf("%d", int64(f))
	}
	return fmt.Sprintf("%v", f)
}