// Copyright 2019 Yunion
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package sqlchemy

import (
	"database/sql"
	"fmt"
	"strings"

	"yunion.io/x/log"
	"yunion.io/x/pkg/errors"
)

// SUnionQueryField represents a field of a union query
type SUnionQueryField struct {
	union *SUnion
	name  string
	alias string
}

// Expression implementation of SUnionQueryField for IQueryField
func (sqf *SUnionQueryField) Expression() string {
	qChar := sqf.union.database().backend.QuoteChar()
	return fmt.Sprintf("%s%s%s.%s%s%s", qChar, sqf.union.Alias(), qChar, qChar, sqf.name, qChar)
}

// Name implementation of SUnionQueryField for IQueryField
func (sqf *SUnionQueryField) Name() string {
	if len(sqf.alias) > 0 {
		return sqf.alias
	}
	return sqf.name
}

// Reference implementation of SUnionQueryField for IQueryField
func (sqf *SUnionQueryField) Reference() string {
	qChar := sqf.union.database().backend.QuoteChar()

	return fmt.Sprintf("%s%s%s.%s%s%s", qChar, sqf.union.Alias(), qChar, qChar, sqf.Name(), qChar)
}

// Label implementation of SUnionQueryField for IQueryField
func (sqf *SUnionQueryField) Label(label string) IQueryField {
	if len(label) > 0 {
		nsqf := *sqf
		nsqf.alias = label
		return &nsqf
	} else {
		return sqf
	}
}

// Variables implementation of SUnionQueryField for IQueryField
func (sqf *SUnionQueryField) Variables() []interface{} {
	return nil
}

// ConvertFromValue implementation of SUnionQueryField for IQueryField
func (sqf *SUnionQueryField) ConvertFromValue(val interface{}) interface{} {
	for _, query := range sqf.union.queries {
		field := query.Field(sqf.name)
		if field != nil {
			return field.ConvertFromValue(val)
		}
	}
	return val
}

func (sqf *SUnionQueryField) database() *SDatabase {
	return sqf.union.database()
}

// SUnion is the struct to store state of a Union query, which implementation the interface of IQuerySource
type SUnion struct {
	alias   string
	queries []IQuery
	fields  []IQueryField
	// orderBy []sQueryOrder
	// limit   int
	// offset  int

	isAll bool
}

// Alias implementation of SUnion for IQuerySource
func (uq *SUnion) Alias() string {
	return uq.alias
}

func (uq *SUnion) operator() string {
	if uq.isAll {
		return uq.database().backend.UnionAllString()
	} else {
		return uq.database().backend.UnionDistinctString()
	}
}

// Expression implementation of SUnion for IQuerySource
func (uq *SUnion) Expression() string {
	var buf strings.Builder
	buf.WriteString("(")
	for i := range uq.queries {
		if i != 0 {
			buf.WriteByte(' ')
			buf.WriteString(uq.operator())
			buf.WriteByte(' ')
		}
		subQ := uq.queries[i].SubQuery()
		buf.WriteString(subQ.Query().String())
	}
	/*if uq.orderBy != nil && len(uq.orderBy) > 0 {
		buf.WriteString(" ORDER BY ")
		for i, f := range uq.orderBy {
			if i > 0 {
				buf.WriteString(", ")
			}
			buf.WriteString(fmt.Sprintf("%s %s", f.field.Reference(), f.order))
		}
	}
	if uq.limit > 0 {
		buf.WriteString(fmt.Sprintf(" LIMIT %d", uq.limit))
	}
	if uq.offset > 0 {
		buf.WriteString(fmt.Sprintf(" OFFSET %d", uq.offset))
	}*/
	buf.WriteByte(')')
	return buf.String()
}

/*func (tq *SUnion) _orderBy(order QueryOrderType, fields []IQueryField) *SUnion {
	if tq.orderBy == nil {
		tq.orderBy = make([]SQueryOrder, 0)
	}
	for _, f := range fields {
		tq.orderBy = append(tq.orderBy, SQueryOrder{field: f, order: order})
	}
	return tq
}

func (tq *SUnion) Asc(fields ...interface{}) *SUnion {
	return tq._orderBy(SQL_ORDER_ASC, convertQueryField(tq, fields))
}

func (tq *SUnion) Desc(fields ...interface{}) *SUnion {
	return tq._orderBy(SQL_ORDER_DESC, convertQueryField(tq, fields))
}
*/

// Limit adds limit to a union query
// func (uq *SUnion) Limit(limit int) *SUnion {
//	uq.limit = limit
//	return uq
// }

// Offset adds offset to a union query
// func (uq *SUnion) Offset(offset int) *SUnion {
// 	uq.offset = offset
//	return uq
// }

// Fields implementation of SUnion for IQuerySource
func (uq *SUnion) Fields() []IQueryField {
	return uq.fields
}

// Field implementation of SUnion for IQuerySource
func (uq *SUnion) Field(name string, alias ...string) IQueryField {
	for i := range uq.fields {
		if name == uq.fields[i].Name() {
			if len(alias) > 0 {
				uq.fields[i].Label(alias[0])
			}
			return uq.fields[i]
		}
	}
	return nil
}

// Variables implementation of SUnion for IQuerySource
func (uq *SUnion) Variables() []interface{} {
	ret := make([]interface{}, 0)
	for i := range uq.queries {
		ret = append(ret, uq.queries[i].Variables()...)
	}
	return ret
}

// Database implementation of SUnion for IQUerySource
func (uq *SUnion) database() *SDatabase {
	for _, q := range uq.queries {
		db := q.database()
		if db != nil {
			return db
		}
	}
	return nil
}

// Union method returns union query of several queries.
// Require the fields of all queries should exactly match
// deprecated
func Union(query ...IQuery) *SUnion {
	u, err := UnionWithError(query...)
	if err != nil {
		log.Fatalf("Fatal: %s", err.Error())
	}
	return u
}

// UnionWithError constructs union query of several Queries
// Require the fields of all queries should exactly match
func UnionWithError(query ...IQuery) (*SUnion, error) {
	return unionWithError(false, query...)
}

func UnionAllWithError(query ...IQuery) (*SUnion, error) {
	return unionWithError(true, query...)
}

func unionWithError(isAll bool, query ...IQuery) (*SUnion, error) {
	if len(query) == 0 {
		return nil, errors.Wrap(sql.ErrNoRows, "empty union query")
	}

	fieldNames := make([]string, 0)
	for _, f := range query[0].QueryFields() {
		fieldNames = append(fieldNames, f.Name())
	}

	var db *SDatabase
	for i := 1; i < len(query); i++ {
		if db == nil {
			db = query[i].database()
		} else if db != query[i].database() {
			panic(ErrUnionAcrossDatabases)
		}
		qfields := query[i].QueryFields()
		if len(fieldNames) != len(qfields) {
			return nil, errors.Wrap(ErrUnionFieldsNotMatch, "number not match")
		}
		for i := range qfields {
			if fieldNames[i] != qfields[i].Name() {
				return nil, errors.Wrapf(ErrUnionFieldsNotMatch, "name %s:%s not match", fieldNames[i], qfields[i].Name())
			}
		}
	}

	fields := make([]IQueryField, len(fieldNames))

	uq := &SUnion{
		alias:   getTableAliasName(),
		queries: query,
		fields:  fields,
		isAll:   isAll,
	}

	for i := range fieldNames {
		fields[i] = &SUnionQueryField{name: fieldNames[i], union: uq}
	}

	return uq, nil
}

// Query of SUnion returns a SQuery of a union query
func (uq *SUnion) Query(f ...IQueryField) *SQuery {
	return DoQuery(uq, f...)
}