package wrapper

import (
	"gitee.com/h79/goutils/dao/option"
	"strings"
)

var _ IFrom = (*From)(nil)
var gFromBuilder FromBuilder

type FromBuilder func(table string, opts ...option.Option) (IFrom, bool)

// SetFromBuilder 表名检测，比如名称为 virtual表，返回真名表名是一个子查询
func SetFromBuilder(fn FromBuilder) {
	gFromBuilder = fn
}

type From struct {
	_from IFrom  // for virtual table
	From  string `json:"from" yaml:"from"`
	As    string `json:"as" yaml:"as"`
}

func (f *From) Reset() {
	f._from = nil
	f.From = ""
	f.As = ""
}

func (f *From) SetAs(as string) {
	f.As = as
}

func (f *From) Is() bool {
	return f.From != ""
}

func (f *From) Build(opts ...option.Option) string {
	if !f.Is() {
		return ""
	}
	table := f.getTableName(opts...)
	child := f.checkChild(table)
	builder := strings.Builder{}
	builder.WriteString(" FROM ")
	if child {
		builder.WriteByte('(')
	}
	f.from(&builder, table, child)
	if child {
		builder.WriteByte(')')
	}
	if f.As != table {
		AddAlias(&builder, f.As)
	}
	return builder.String()
}

func (f *From) from(builder *strings.Builder, table string, child bool) bool {
	quo := !child
	first := table[0]
	end := table[len(table)-1]
	if first == '`' {
		quo = false
	}
	if quo {
		builder.WriteByte('`')
		first = '`'
	}
	builder.WriteString(table)
	if first == '`' && end != '`' {
		builder.WriteByte('`')
	}
	return true
}

func (f *From) getTableName(opts ...option.Option) string {
	if gFromBuilder == nil {
		return f.From
	}
	if f._from == nil {
		from, ok := gFromBuilder(f.From, opts...)
		if ok && from != nil {
			f._from = from
		}
	}
	if f._from != nil {
		return f._from.Build(opts...)
	}
	return f.From
}

func (f *From) checkChild(table string) bool {
	fm := strings.TrimSpace(table)
	fm = strings.TrimLeft(fm, "(")
	l := len(fm)
	if l > 9 {
		l = 9
	}
	up := strings.ToUpper(fm[0:l])
	if strings.Contains(up, "DROP") ||
		strings.Contains(up, "DELETE") ||
		strings.Contains(up, "ALTER") ||
		strings.Contains(up, "INSERT") {
		strings.Contains(up, "UPDATE")
		panic("may be illegal，lead to serious consequences")
	}
	return strings.Contains(up, "SELECT")
}