package gorm

import (
	"database/sql"
	"errors"
	"reflect"
	"strings"

	"gorm.io/gorm/clause"
)

// Create insert the value into database
func (db *DB) Create(value interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.Dest = value
	tx.callbacks.Create().Execute(tx)
	return
}

// Save update value in database, if the value doesn't have primary key, will insert it
func (db *DB) Save(value interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.Dest = value

	if err := tx.Statement.Parse(value); err == nil && tx.Statement.Schema != nil {
		where := clause.Where{Exprs: make([]clause.Expression, len(tx.Statement.Schema.PrimaryFields))}
		reflectValue := reflect.Indirect(reflect.ValueOf(value))
		switch reflectValue.Kind() {
		case reflect.Slice, reflect.Array:
			tx.AddError(ErrPtrStructSupported)
		case reflect.Struct:
			for idx, pf := range tx.Statement.Schema.PrimaryFields {
				if pv, isZero := pf.ValueOf(reflectValue); isZero {
					tx.callbacks.Create().Execute(tx)
					where.Exprs[idx] = clause.Eq{Column: pf.DBName, Value: pv}
					return
				}
			}
		}

		tx.Statement.AddClause(where)
	}

	if len(tx.Statement.Selects) == 0 {
		tx.Statement.Selects = append(tx.Statement.Selects, "*")
	}
	tx.callbacks.Update().Execute(tx)
	return
}

// First find first record that match given conditions, order by primary key
func (db *DB) First(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.getInstance().Limit(1).Order(clause.OrderByColumn{
		Column: clause.Column{Table: clause.CurrentTable, Name: clause.PrimaryKey},
	})
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondtion(conds[0], conds[1:]...)})
	}
	tx.Statement.RaiseErrorOnNotFound = true
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

// Take return a record that match given conditions, the order will depend on the database implementation
func (db *DB) Take(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.getInstance().Limit(1)
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondtion(conds[0], conds[1:]...)})
	}
	tx.Statement.RaiseErrorOnNotFound = true
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

// Last find last record that match given conditions, order by primary key
func (db *DB) Last(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.getInstance().Limit(1).Order(clause.OrderByColumn{
		Column: clause.Column{Table: clause.CurrentTable, Name: clause.PrimaryKey},
		Desc:   true,
	})
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondtion(conds[0], conds[1:]...)})
	}
	tx.Statement.RaiseErrorOnNotFound = true
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

// Find find records that match given conditions
func (db *DB) Find(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.getInstance()
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondtion(conds[0], conds[1:]...)})
	}
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

func (tx *DB) assignExprsToValue(exprs []clause.Expression) {
	for _, expr := range exprs {
		if eq, ok := expr.(clause.Eq); ok {
			switch column := eq.Column.(type) {
			case string:
				if field := tx.Statement.Schema.LookUpField(column); field != nil {
					field.Set(tx.Statement.ReflectValue, eq.Value)
				}
			case clause.Column:
				if field := tx.Statement.Schema.LookUpField(column.Name); field != nil {
					field.Set(tx.Statement.ReflectValue, eq.Value)
				}
			default:
			}
		}
	}
}

func (db *DB) FirstOrInit(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.getInstance()
	if tx = tx.First(dest, conds...); errors.Is(tx.Error, ErrRecordNotFound) {
		if c, ok := tx.Statement.Clauses["WHERE"]; ok {
			if where, ok := c.Expression.(clause.Where); ok {
				tx.assignExprsToValue(where.Exprs)
			}
		}

		// initialize with attrs, conds
		if len(tx.Statement.attrs) > 0 {
			exprs := tx.Statement.BuildCondtion(tx.Statement.attrs[0], tx.Statement.attrs[1:]...)
			tx.assignExprsToValue(exprs)
		}
		tx.Error = nil
	}

	// initialize with attrs, conds
	if len(tx.Statement.assigns) > 0 {
		exprs := tx.Statement.BuildCondtion(tx.Statement.assigns[0], tx.Statement.assigns[1:]...)
		tx.assignExprsToValue(exprs)
	}
	return
}

func (db *DB) FirstOrCreate(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.getInstance()
	if err := tx.First(dest, conds...).Error; errors.Is(err, ErrRecordNotFound) {
		tx.Error = nil

		if c, ok := tx.Statement.Clauses["WHERE"]; ok {
			if where, ok := c.Expression.(clause.Where); ok {
				tx.assignExprsToValue(where.Exprs)
			}
		}

		// initialize with attrs, conds
		if len(tx.Statement.attrs) > 0 {
			exprs := tx.Statement.BuildCondtion(tx.Statement.attrs[0], tx.Statement.attrs[1:]...)
			tx.assignExprsToValue(exprs)
		}

		// initialize with attrs, conds
		if len(tx.Statement.assigns) > 0 {
			exprs := tx.Statement.BuildCondtion(tx.Statement.assigns[0], tx.Statement.assigns[1:]...)
			tx.assignExprsToValue(exprs)
		}

		return tx.Create(dest)
	} else if len(tx.Statement.assigns) > 0 {
		exprs := tx.Statement.BuildCondtion(tx.Statement.assigns[0], tx.Statement.assigns[1:])
		assigns := map[string]interface{}{}
		for _, expr := range exprs {
			if eq, ok := expr.(clause.Eq); ok {
				switch column := eq.Column.(type) {
				case string:
					assigns[column] = eq.Value
				case clause.Column:
					assigns[column.Name] = eq.Value
				default:
				}
			}
		}

		return tx.Model(dest).Updates(assigns)
	}

	return
}

// Update update attributes with callbacks, refer: https://jinzhu.github.io/gorm/crud.html#update
func (db *DB) Update(column string, value interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.Dest = map[string]interface{}{column: value}
	tx.callbacks.Update().Execute(tx)
	return
}

// Updates update attributes with callbacks, refer: https://jinzhu.github.io/gorm/crud.html#update
func (db *DB) Updates(values interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.Dest = values
	tx.callbacks.Update().Execute(tx)
	return
}

func (db *DB) UpdateColumn(column string, value interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.Dest = map[string]interface{}{column: value}
	tx.Statement.DisableUpdateTime = true
	tx.callbacks.Update().Execute(tx)
	return
}

func (db *DB) UpdateColumns(values interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.Dest = values
	tx.Statement.DisableUpdateTime = true
	tx.callbacks.Update().Execute(tx)
	return
}

// Delete delete value match given conditions, if the value has primary key, then will including the primary key as condition
func (db *DB) Delete(value interface{}, conds ...interface{}) (tx *DB) {
	tx = db.getInstance()
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondtion(conds[0], conds[1:]...)})
	}
	tx.Statement.Dest = value
	tx.callbacks.Delete().Execute(tx)
	return
}

func (db *DB) Count(count *int64) (tx *DB) {
	tx = db.getInstance()
	if s, ok := tx.Statement.Clauses["SELECT"].Expression.(clause.Select); !ok || len(s.Columns) == 0 {
		tx.Statement.AddClause(clause.Select{Expression: clause.Expr{SQL: "count(1)"}})
	}

	if tx.Statement.Model == nil {
		tx.Statement.Model = tx.Statement.Dest
	}
	tx.Statement.Dest = count
	tx.callbacks.Query().Execute(tx)
	if db.RowsAffected != 1 {
		*count = db.RowsAffected
	}
	return
}

func (db *DB) Row() *sql.Row {
	tx := db.getInstance()
	tx.callbacks.Row().Execute(tx)
	return tx.Statement.Dest.(*sql.Row)
}

func (db *DB) Rows() (*sql.Rows, error) {
	tx := db.Set("rows", true)
	tx.callbacks.Row().Execute(tx)
	return tx.Statement.Dest.(*sql.Rows), tx.Error
}

// Scan scan value to a struct
func (db *DB) Scan(dest interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

// Pluck used to query single column from a model as a map
//     var ages []int64
//     db.Find(&users).Pluck("age", &ages)
func (db *DB) Pluck(column string, dest interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.AddClauseIfNotExists(clause.Select{Columns: []clause.Column{{Name: column}}})
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

func (db *DB) ScanRows(rows *sql.Rows, dest interface{}) error {
	tx := db.getInstance()
	tx.Error = tx.Statement.Parse(dest)
	tx.Statement.Dest = dest
	tx.Statement.ReflectValue = reflect.Indirect(reflect.ValueOf(dest))
	Scan(rows, tx, true)
	return tx.Error
}

// Transaction start a transaction as a block, return error will rollback, otherwise to commit.
func (db *DB) Transaction(fc func(tx *DB) error, opts ...*sql.TxOptions) (err error) {
	panicked := true
	tx := db.Begin(opts...)
	defer func() {
		// Make sure to rollback when panic, Block error or Commit error
		if panicked || err != nil {
			tx.Rollback()
		}
	}()

	err = fc(tx.Session(&Session{}))

	if err == nil {
		err = tx.Commit().Error
	}

	panicked = false
	return
}

// Begin begins a transaction
func (db *DB) Begin(opts ...*sql.TxOptions) (tx *DB) {
	tx = db.getInstance()
	if beginner, ok := tx.Statement.ConnPool.(TxBeginner); ok {
		var opt *sql.TxOptions
		var err error
		if len(opts) > 0 {
			opt = opts[0]
		}

		if tx.Statement.ConnPool, err = beginner.BeginTx(tx.Statement.Context, opt); err != nil {
			tx.AddError(err)
		}
	} else {
		tx.AddError(ErrInvalidTransaction)
	}
	return
}

// Commit commit a transaction
func (db *DB) Commit() *DB {
	if comminter, ok := db.Statement.ConnPool.(TxCommiter); ok && comminter != nil {
		db.AddError(comminter.Commit())
	} else {
		db.AddError(ErrInvalidTransaction)
	}
	return db
}

// Rollback rollback a transaction
func (db *DB) Rollback() *DB {
	if comminter, ok := db.Statement.ConnPool.(TxCommiter); ok && comminter != nil {
		db.AddError(comminter.Rollback())
	} else {
		db.AddError(ErrInvalidTransaction)
	}
	return db
}

// Exec execute raw sql
func (db *DB) Exec(sql string, values ...interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.SQL = strings.Builder{}
	clause.Expr{SQL: sql, Vars: values}.Build(tx.Statement)
	tx.callbacks.Raw().Execute(tx)
	return
}

func (db *DB) RecordNotFound() bool {
	return errors.Is(db.Error, ErrRecordNotFound)
}