// Copyright 2019 The Xorm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package dialects

import (
	"context"
	"fmt"
	"strings"
	"time"

	"xorm.io/xorm/core"
	"xorm.io/xorm/schemas"
)

type URI struct {
	DBType  schemas.DBType
	Proto   string
	Host    string
	Port    string
	DBName  string
	User    string
	Passwd  string
	Charset string
	Laddr   string
	Raddr   string
	Timeout time.Duration
	Schema  string
}

// Dialect represents a kind of database
type Dialect interface {
	Init(*core.DB, *URI) error
	URI() *URI
	DB() *core.DB
	DBType() schemas.DBType
	SQLType(*schemas.Column) string
	FormatBytes(b []byte) string
	DefaultSchema() string

	IsReserved(string) bool
	Quoter() schemas.Quoter
	SetQuotePolicy(quotePolicy QuotePolicy)

	AutoIncrStr() string

	SupportInsertMany() bool
	SupportEngine() bool
	SupportCharset() bool
	SupportDropIfExists() bool
	IndexOnTable() bool
	ShowCreateNull() bool

	IndexCheckSQL(tableName, idxName string) (string, []interface{})
	TableCheckSQL(tableName string) (string, []interface{})

	IsColumnExist(ctx context.Context, tableName string, colName string) (bool, error)

	CreateTableSQL(table *schemas.Table, tableName, storeEngine, charset string) string
	DropTableSQL(tableName string) string
	CreateIndexSQL(tableName string, index *schemas.Index) string
	DropIndexSQL(tableName string, index *schemas.Index) string

	AddColumnSQL(tableName string, col *schemas.Column) string
	ModifyColumnSQL(tableName string, col *schemas.Column) string

	ForUpdateSQL(query string) string

	GetColumns(ctx context.Context, tableName string) ([]string, map[string]*schemas.Column, error)
	GetTables(ctx context.Context) ([]*schemas.Table, error)
	GetIndexes(ctx context.Context, tableName string) (map[string]*schemas.Index, error)

	Filters() []Filter
	SetParams(params map[string]string)
}

// Base represents a basic dialect and all real dialects could embed this struct
type Base struct {
	db      *core.DB
	dialect Dialect
	uri     *URI
	quoter  schemas.Quoter
}

func (b *Base) Quoter() schemas.Quoter {
	return b.quoter
}

func (b *Base) DB() *core.DB {
	return b.db
}

func (b *Base) DefaultSchema() string {
	return ""
}

func (b *Base) Init(db *core.DB, dialect Dialect, uri *URI) error {
	b.db, b.dialect, b.uri = db, dialect, uri
	return nil
}

func (b *Base) URI() *URI {
	return b.uri
}

func (b *Base) DBType() schemas.DBType {
	return b.uri.DBType
}

// String generate column description string according dialect
func (b *Base) String(col *schemas.Column) string {
	sql := b.dialect.Quoter().Quote(col.Name) + " "

	sql += b.dialect.SQLType(col) + " "

	if col.IsPrimaryKey {
		sql += "PRIMARY KEY "
		if col.IsAutoIncrement {
			sql += b.dialect.AutoIncrStr() + " "
		}
	}

	if col.Default != "" {
		sql += "DEFAULT " + col.Default + " "
	}

	if b.dialect.ShowCreateNull() {
		if col.Nullable {
			sql += "NULL "
		} else {
			sql += "NOT NULL "
		}
	}

	return sql
}

// StringNoPk generate column description string according dialect without primary keys
func (b *Base) StringNoPk(col *schemas.Column) string {
	sql := b.dialect.Quoter().Quote(col.Name) + " "

	sql += b.dialect.SQLType(col) + " "

	if col.Default != "" {
		sql += "DEFAULT " + col.Default + " "
	}

	if b.dialect.ShowCreateNull() {
		if col.Nullable {
			sql += "NULL "
		} else {
			sql += "NOT NULL "
		}
	}

	return sql
}

func (b *Base) FormatBytes(bs []byte) string {
	return fmt.Sprintf("0x%x", bs)
}

func (b *Base) ShowCreateNull() bool {
	return true
}

func (db *Base) SupportDropIfExists() bool {
	return true
}

func (db *Base) DropTableSQL(tableName string) string {
	quote := db.dialect.Quoter().Quote
	return fmt.Sprintf("DROP TABLE IF EXISTS %s", quote(tableName))
}

func (db *Base) HasRecords(ctx context.Context, query string, args ...interface{}) (bool, error) {
	rows, err := db.DB().QueryContext(ctx, query, args...)
	if err != nil {
		return false, err
	}
	defer rows.Close()

	if rows.Next() {
		return true, nil
	}
	return false, nil
}

func (db *Base) IsColumnExist(ctx context.Context, tableName, colName string) (bool, error) {
	quote := db.dialect.Quoter().Quote
	query := fmt.Sprintf(
		"SELECT %v FROM %v.%v WHERE %v = ? AND %v = ? AND %v = ?",
		quote("COLUMN_NAME"),
		quote("INFORMATION_SCHEMA"),
		quote("COLUMNS"),
		quote("TABLE_SCHEMA"),
		quote("TABLE_NAME"),
		quote("COLUMN_NAME"),
	)
	return db.HasRecords(ctx, query, db.uri.DBName, tableName, colName)
}

func (db *Base) AddColumnSQL(tableName string, col *schemas.Column) string {
	return fmt.Sprintf("ALTER TABLE %v ADD %v", db.dialect.Quoter().Quote(tableName),
		db.String(col))
}

func (db *Base) CreateIndexSQL(tableName string, index *schemas.Index) string {
	quoter := db.dialect.Quoter()
	var unique string
	var idxName string
	if index.Type == schemas.UniqueType {
		unique = " UNIQUE"
	}
	idxName = index.XName(tableName)
	return fmt.Sprintf("CREATE%s INDEX %v ON %v (%v)", unique,
		quoter.Quote(idxName), quoter.Quote(tableName),
		quoter.Join(index.Cols, ","))
}

func (db *Base) DropIndexSQL(tableName string, index *schemas.Index) string {
	quote := db.dialect.Quoter().Quote
	var name string
	if index.IsRegular {
		name = index.XName(tableName)
	} else {
		name = index.Name
	}
	return fmt.Sprintf("DROP INDEX %v ON %s", quote(name), quote(tableName))
}

func (db *Base) ModifyColumnSQL(tableName string, col *schemas.Column) string {
	return fmt.Sprintf("alter table %s MODIFY COLUMN %s", tableName, db.StringNoPk(col))
}

func (b *Base) CreateTableSQL(table *schemas.Table, tableName, storeEngine, charset string) string {
	var sql string
	sql = "CREATE TABLE IF NOT EXISTS "
	if tableName == "" {
		tableName = table.Name
	}

	quoter := b.dialect.Quoter()
	sql += quoter.Quote(tableName)
	sql += " ("

	if len(table.ColumnsSeq()) > 0 {
		pkList := table.PrimaryKeys

		for _, colName := range table.ColumnsSeq() {
			col := table.GetColumn(colName)
			if col.IsPrimaryKey && len(pkList) == 1 {
				sql += b.String(col)
			} else {
				sql += b.StringNoPk(col)
			}
			sql = strings.TrimSpace(sql)
			if b.DBType() == schemas.MYSQL && len(col.Comment) > 0 {
				sql += " COMMENT '" + col.Comment + "'"
			}
			sql += ", "
		}

		if len(pkList) > 1 {
			sql += "PRIMARY KEY ( "
			sql += quoter.Join(pkList, ",")
			sql += " ), "
		}

		sql = sql[:len(sql)-2]
	}
	sql += ")"

	if b.dialect.SupportEngine() && storeEngine != "" {
		sql += " ENGINE=" + storeEngine
	}
	if b.dialect.SupportCharset() {
		if len(charset) == 0 {
			charset = b.dialect.URI().Charset
		}
		if len(charset) > 0 {
			sql += " DEFAULT CHARSET " + charset
		}
	}

	return sql
}

func (b *Base) ForUpdateSQL(query string) string {
	return query + " FOR UPDATE"
}

func (b *Base) SetParams(params map[string]string) {
}

var (
	dialects = map[string]func() Dialect{}
)

// RegisterDialect register database dialect
func RegisterDialect(dbName schemas.DBType, dialectFunc func() Dialect) {
	if dialectFunc == nil {
		panic("core: Register dialect is nil")
	}
	dialects[strings.ToLower(string(dbName))] = dialectFunc // !nashtsai! allow override dialect
}

// QueryDialect query if registered database dialect
func QueryDialect(dbName schemas.DBType) Dialect {
	if d, ok := dialects[strings.ToLower(string(dbName))]; ok {
		return d()
	}
	return nil
}

func regDrvsNDialects() bool {
	providedDrvsNDialects := map[string]struct {
		dbType     schemas.DBType
		getDriver  func() Driver
		getDialect func() Dialect
	}{
		"mssql":    {"mssql", func() Driver { return &odbcDriver{} }, func() Dialect { return &mssql{} }},
		"odbc":     {"mssql", func() Driver { return &odbcDriver{} }, func() Dialect { return &mssql{} }}, // !nashtsai! TODO change this when supporting MS Access
		"mysql":    {"mysql", func() Driver { return &mysqlDriver{} }, func() Dialect { return &mysql{} }},
		"mymysql":  {"mysql", func() Driver { return &mymysqlDriver{} }, func() Dialect { return &mysql{} }},
		"postgres": {"postgres", func() Driver { return &pqDriver{} }, func() Dialect { return &postgres{} }},
		"pgx":      {"postgres", func() Driver { return &pqDriverPgx{} }, func() Dialect { return &postgres{} }},
		"sqlite3":  {"sqlite3", func() Driver { return &sqlite3Driver{} }, func() Dialect { return &sqlite3{} }},
		"oci8":     {"oracle", func() Driver { return &oci8Driver{} }, func() Dialect { return &oracle{} }},
		"goracle":  {"oracle", func() Driver { return &goracleDriver{} }, func() Dialect { return &oracle{} }},
	}

	for driverName, v := range providedDrvsNDialects {
		if driver := QueryDriver(driverName); driver == nil {
			RegisterDriver(driverName, v.getDriver())
			RegisterDialect(v.dbType, v.getDialect)
		}
	}
	return true
}

func init() {
	regDrvsNDialects()
}