package query

import (
	"gorm.io/gorm"
	"strings"
)

type Query struct {
	db        *gorm.DB
	condition string
	fields    []string
	params    []interface{}
	limit     int
	offset    int
	table     string
	orderBy   []string
	groupBy   []string
	joins     []join
}

type join struct {
	Table     string
	Direction string
	Conds     []*Condition
}

func (query *Query) Select(fields ...string) *Query {
	if query.fields == nil {
		query.fields = fields
	} else {
		query.fields = append(query.fields, fields...)
	}
	return query
}

func (query *Query) From(table string) *Query {
	query.table = table
	return query
}

//// Joins specify Joins conditions
////     db.Joins("JOIN emails ON emails.user_id = users.id AND emails.email = ?", "jinzhu@example.org").Find(&user)
//func (s *DB) Joins(query string, args ...interface{}) *DB {
//	return s.clone().search.Joins(query, args...).db
//}
func (query *Query) LeftJoin(table string, conds ...*Condition) *Query {
	query.joins = append(query.joins, join{
		Table:     table,
		Direction: "LEFT",
		Conds:     conds,
	})
	return query
}

func (query *Query) RightJoin(table string, conds ...*Condition) *Query {
	query.joins = append(query.joins, join{
		Table:     table,
		Direction: "RIGHT",
		Conds:     conds,
	})
	return query
}

func (query *Query) InnerJoin(table string, conds ...*Condition) *Query {
	query.joins = append(query.joins, join{
		Table:     table,
		Direction: "INNER",
		Conds:     conds,
	})
	return query
}

func (query *Query) AndFilterWhere(conds ...*Condition) *Query {
	length := len(conds)
	if length == 0 {
		return query
	}
	cs, ps := buildConditions("AND", true, conds...)
	if cs == "" {
		return query
	}
	query.params = append(query.params, ps...)
	if query.condition == "" {
		query.condition = cs
	} else {
		query.condition += " AND " + cs
	}
	return query
}

func (query *Query) AndWhere(conds ...*Condition) *Query {
	length := len(conds)
	if length == 0 {
		return query
	}
	cs, ps := buildConditions("AND", false, conds...)
	if cs == "" {
		return query
	}
	query.params = append(query.params, ps...)
	if query.condition == "" {
		query.condition = cs
	} else {
		query.condition += " AND " + cs
	}
	return query
}

func (query *Query) OrFilterWhere(conds ...*Condition) *Query {
	length := len(conds)
	if length == 0 {
		return query
	}
	cs, ps := buildConditions("OR", true, conds...)
	if cs == "" {
		return query
	}
	query.params = append(query.params, ps...)
	if query.condition == "" {
		query.condition = cs
	} else {
		query.condition += " AND (" + cs + ")"
	}
	return query
}

func (query *Query) OrWhere(conds ...*Condition) *Query {
	length := len(conds)
	if length == 0 {
		return query
	}
	cs, ps := buildConditions("OR", false, conds...)
	if cs == "" {
		return query
	}
	query.params = append(query.params, ps...)
	if query.condition == "" {
		query.condition = cs
	} else {
		query.condition += " AND (" + cs + ")"
	}
	return query
}

func (query *Query) GroupBy(cols ...string) *Query {
	query.groupBy = append(query.groupBy, cols...)
	return query
}

func (query *Query) OrderBy(col, direction string) *Query {
	direction = strings.ToUpper(direction)
	if direction == "" || !(direction == "ASC" || direction == "DESC") {
		direction = "ASC"
	}
	query.orderBy = append(query.orderBy, col+" "+direction)
	return query
}

func (query *Query) Offset(i int) *Query {
	query.offset = i
	return query
}

func (query *Query) Limit(i int) *Query {
	query.limit = i
	return query
}

func (query *Query) prepare() (*gorm.DB, error) {
	db := query.db
	if query.condition != "" {
		db = db.Where(query.condition, query.params...)
	}
	if query.fields != nil {
		db = db.Select(strings.Join(query.fields, ","))
	}
	if query.table != "" {
		db = db.Table(query.table)
	}
	if query.joins != nil && len(query.joins) > 0 {
		for _, joinEntity := range query.joins {
			cs, ps := buildConditions("OR", false, joinEntity.Conds...)
			db = db.Joins(joinEntity.Direction+" JOIN "+joinEntity.Table+" ON "+cs, ps...)
		}
	}
	if query.orderBy != nil && len(query.orderBy) > 0 {
		db = db.Order(strings.Join(query.orderBy, ","))
	}
	if query.groupBy != nil && len(query.groupBy) > 0 {
		db = db.Group(strings.Join(query.groupBy, ","))
	}
	if query.offset > 0 {
		db = db.Offset(query.offset)
	}
	if query.limit > 0 {
		db = db.Limit(query.limit)
	}
	return db, nil
}

func (query *Query) Count(v interface{}) (i int64) {
	var (
		db  *gorm.DB
		err error
	)
	if db, err = query.prepare(); err != nil {
		return
	} else {
		err = db.Model(v).Count(&i).Error
	}
	return
}

func (query *Query) One(v interface{}) (err error) {
	var (
		db *gorm.DB
	)
	if db, err = query.prepare(); err != nil {
		return
	} else {
		err = db.First(v).Error
	}
	return
}

func (query *Query) All(v interface{}) (err error) {
	var (
		db *gorm.DB
	)
	if db, err = query.prepare(); err != nil {
		return
	} else {
		err = db.Find(v).Error
	}
	return
}

func New(db *gorm.DB) *Query {
	return &Query{
		db:      db,
		params:  make([]interface{}, 0),
		orderBy: make([]string, 0),
		groupBy: make([]string, 0),
		joins:   make([]join, 0),
	}
}