package postgres

import (
	"fmt"

	"github.com/jinzhu/gorm"
	"github.com/jinzhu/gorm/clause"
	"github.com/jinzhu/gorm/migrator"
	"github.com/jinzhu/gorm/schema"
)

type Migrator struct {
	migrator.Migrator
}

func (m Migrator) CurrentDatabase() (name string) {
	m.DB.Raw("SELECT CURRENT_DATABASE()").Row().Scan(&name)
	return
}

func (m Migrator) BuildIndexOptions(opts []schema.IndexOption, stmt *gorm.Statement) (results []interface{}) {
	for _, opt := range opts {
		str := stmt.Quote(opt.DBName)
		if opt.Expression != "" {
			str = opt.Expression
		}

		if opt.Collate != "" {
			str += " COLLATE " + opt.Collate
		}

		if opt.Sort != "" {
			str += " " + opt.Sort
		}
		results = append(results, clause.Expr{SQL: str})
	}
	return
}

func (m Migrator) HasIndex(value interface{}, indexName string) bool {
	var count int64
	m.RunWithValue(value, func(stmt *gorm.Statement) error {
		return m.DB.Raw(
			"SELECT count(*) FROM pg_indexes WHERE tablename = ? AND indexname = ? AND schemaname = CURRENT_SCHEMA()", stmt.Table, indexName,
		).Row().Scan(&count)
	})

	return count > 0
}

func (m Migrator) CreateIndex(value interface{}, name string) error {
	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
		err := fmt.Errorf("failed to create index with name %v", name)
		indexes := stmt.Schema.ParseIndexes()

		if idx, ok := indexes[name]; ok {
			opts := m.BuildIndexOptions(idx.Fields, stmt)
			values := []interface{}{clause.Column{Name: idx.Name}, clause.Table{Name: stmt.Table}, opts}

			createIndexSQL := "CREATE "
			if idx.Class != "" {
				createIndexSQL += idx.Class + " "
			}
			createIndexSQL += "INDEX ?"

			if idx.Type != "" {
				createIndexSQL += " USING " + idx.Type
			}
			createIndexSQL += " ON ??"

			if idx.Where != "" {
				createIndexSQL += " WHERE " + idx.Where
			}

			return m.DB.Exec(createIndexSQL, values...).Error
		} else if field := stmt.Schema.LookUpField(name); field != nil {
			for _, idx := range indexes {
				for _, idxOpt := range idx.Fields {
					if idxOpt.Field == field {
						if err = m.CreateIndex(value, idx.Name); err != nil {
							return err
						}
					}
				}
			}
		}
		return err
	})
}