package mysql

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

	"github.com/go-sql-driver/mysql"
	"github.com/neilotoole/lg"
	"github.com/xo/dburl"

	"github.com/neilotoole/sq/libsq/core/errz"
	"github.com/neilotoole/sq/libsq/core/kind"
	"github.com/neilotoole/sq/libsq/core/sqlz"
	"github.com/neilotoole/sq/libsq/core/stringz"
	"github.com/neilotoole/sq/libsq/driver"
	"github.com/neilotoole/sq/libsq/source"
	"github.com/neilotoole/sq/libsq/sqlbuilder"
	"github.com/neilotoole/sq/libsq/sqlmodel"
)

const (
	// Type is the MySQL source driver type.
	Type = source.Type("mysql")

	// dbDrvr is the backing MySQL SQL driver impl name.
	dbDrvr = "mysql"
)

var _ driver.Provider = (*Provider)(nil)

// Provider is the MySQL implementation of driver.Provider.
type Provider struct {
	Log lg.Log
}

// DriverFor implements driver.Provider.
func (p *Provider) DriverFor(typ source.Type) (driver.Driver, error) {
	if typ != Type {
		return nil, errz.Errorf("unsupported driver type %q", typ)
	}

	return &driveri{log: p.Log}, nil
}

var _ driver.Driver = (*driveri)(nil)

// driveri is the MySQL implementation of driver.Driver.
type driveri struct {
	log lg.Log
}

// DriverMetadata implements driver.Driver.
func (d *driveri) DriverMetadata() driver.Metadata {
	return driver.Metadata{
		Type:        Type,
		Description: "MySQL",
		Doc:         "https://github.com/go-sql-driver/mysql",
		IsSQL:       true,
	}
}

// Dialect implements driver.Driver.
func (d *driveri) Dialect() driver.Dialect {
	return driver.Dialect{
		Type:           Type,
		Placeholders:   placeholders,
		Quote:          '`',
		IntBool:        true,
		MaxBatchValues: 250,
	}
}

func placeholders(numCols, numRows int) string {
	rows := make([]string, numRows)
	for i := 0; i < numRows; i++ {
		rows[i] = "(" + stringz.RepeatJoin("?", numCols, driver.Comma) + ")"
	}
	return strings.Join(rows, driver.Comma)
}

// SQLBuilder implements driver.SQLDriver.
func (d *driveri) SQLBuilder() (sqlbuilder.FragmentBuilder, sqlbuilder.QueryBuilder) {
	return newFragmentBuilder(d.log), &sqlbuilder.BaseQueryBuilder{}
}

// RecordMeta implements driver.SQLDriver.
func (d *driveri) RecordMeta(colTypes []*sql.ColumnType) (sqlz.RecordMeta, driver.NewRecordFunc, error) {
	recMeta := recordMetaFromColumnTypes(d.log, colTypes)
	mungeFn := getNewRecordFunc(recMeta)
	return recMeta, mungeFn, nil
}

// CreateTable implements driver.SQLDriver.
func (d *driveri) CreateTable(ctx context.Context, db sqlz.DB, tblDef *sqlmodel.TableDef) error {
	createStmt, err := buildCreateTableStmt(tblDef)
	if err != nil {
		return err
	}

	_, err = db.ExecContext(ctx, createStmt)
	return errz.Err(err)
}

// AlterTableAddColumn implements driver.SQLDriver.
func (d *driveri) AlterTableAddColumn(ctx context.Context, db *sql.DB, tbl string, col string, kind kind.Kind) error {
	q := fmt.Sprintf("ALTER TABLE %q ADD COLUMN %q ", tbl, col) + dbTypeNameFromKind(kind)

	_, err := db.ExecContext(ctx, q)
	if err != nil {
		return errz.Wrapf(err, "alter table: failed to add column %q to table %q", col, tbl)
	}

	return nil
}

// PrepareInsertStmt implements driver.SQLDriver.
func (d *driveri) PrepareInsertStmt(ctx context.Context, db sqlz.DB, destTbl string, destColNames []string, numRows int) (*driver.StmtExecer, error) {
	destColsMeta, err := d.getTableRecordMeta(ctx, db, destTbl, destColNames)
	if err != nil {
		return nil, err
	}

	stmt, err := driver.PrepareInsertStmt(ctx, d, db, destTbl, destColsMeta.Names(), numRows)
	if err != nil {
		return nil, err
	}

	execer := driver.NewStmtExecer(stmt, newInsertMungeFunc(destTbl, destColsMeta), newStmtExecFunc(stmt), destColsMeta)
	return execer, nil
}

// PrepareUpdateStmt implements driver.SQLDriver.
func (d *driveri) PrepareUpdateStmt(ctx context.Context, db sqlz.DB, destTbl string, destColNames []string, where string) (*driver.StmtExecer, error) {
	destColsMeta, err := d.getTableRecordMeta(ctx, db, destTbl, destColNames)
	if err != nil {
		return nil, err
	}

	query, err := buildUpdateStmt(destTbl, destColNames, where)
	if err != nil {
		return nil, err
	}

	stmt, err := db.PrepareContext(ctx, query)
	if err != nil {
		return nil, err
	}

	execer := driver.NewStmtExecer(stmt, newInsertMungeFunc(destTbl, destColsMeta), newStmtExecFunc(stmt), destColsMeta)
	return execer, nil
}

func newStmtExecFunc(stmt *sql.Stmt) driver.StmtExecFunc {
	return func(ctx context.Context, args ...interface{}) (int64, error) {
		res, err := stmt.ExecContext(ctx, args...)
		if err != nil {
			return 0, errz.Err(err)
		}
		affected, err := res.RowsAffected()
		return affected, errz.Err(err)
	}
}

// CopyTable implements driver.SQLDriver.
func (d *driveri) CopyTable(ctx context.Context, db sqlz.DB, fromTable, toTable string, copyData bool) (int64, error) {
	stmt := fmt.Sprintf("CREATE TABLE IF NOT EXISTS `%s` SELECT * FROM `%s`", toTable, fromTable)

	if !copyData {
		stmt += " WHERE 0"
	}

	affected, err := sqlz.ExecResult(ctx, db, stmt)
	if err != nil {
		return 0, errz.Err(err)
	}

	return affected, nil
}

// DropTable implements driver.SQLDriver.
func (d *driveri) DropTable(ctx context.Context, db sqlz.DB, tbl string, ifExists bool) error {
	var stmt string

	if ifExists {
		stmt = fmt.Sprintf("DROP TABLE IF EXISTS `%s` RESTRICT", tbl)
	} else {
		stmt = fmt.Sprintf("DROP TABLE `%s` RESTRICT", tbl)
	}

	_, err := db.ExecContext(ctx, stmt)
	return errz.Err(err)
}

// TableColumnTypes implements driver.SQLDriver.
func (d *driveri) TableColumnTypes(ctx context.Context, db sqlz.DB, tblName string, colNames []string) ([]*sql.ColumnType, error) {
	const queryTpl = "SELECT %s FROM %s LIMIT 0"

	dialect := d.Dialect()
	quote := string(dialect.Quote)
	tblNameQuoted := stringz.Surround(tblName, quote)

	var colsClause = "*"
	if len(colNames) > 0 {
		colNamesQuoted := stringz.SurroundSlice(colNames, quote)
		colsClause = strings.Join(colNamesQuoted, driver.Comma)
	}

	query := fmt.Sprintf(queryTpl, colsClause, tblNameQuoted)
	rows, err := db.QueryContext(ctx, query)
	if err != nil {
		return nil, errz.Err(err)
	}

	colTypes, err := rows.ColumnTypes()
	if err != nil {
		d.log.WarnIfFuncError(rows.Close)
		return nil, errz.Err(err)
	}

	err = rows.Err()
	if err != nil {
		d.log.WarnIfFuncError(rows.Close)
		return nil, errz.Err(err)
	}

	err = rows.Close()
	if err != nil {
		return nil, errz.Err(err)
	}

	return colTypes, nil
}

func (d *driveri) getTableRecordMeta(ctx context.Context, db sqlz.DB, tblName string, colNames []string) (sqlz.RecordMeta, error) {
	colTypes, err := d.TableColumnTypes(ctx, db, tblName, colNames)
	if err != nil {
		return nil, err
	}

	destCols, _, err := d.RecordMeta(colTypes)
	if err != nil {
		return nil, err
	}

	return destCols, nil
}

// Open implements driver.Driver.
func (d *driveri) Open(ctx context.Context, src *source.Source) (driver.Database, error) {
	dsn, err := dsnFromLocation(src)
	if err != nil {
		return nil, err
	}

	db, err := sql.Open(dbDrvr, dsn)
	if err != nil {
		return nil, errz.Err(err)
	}

	return &database{log: d.log, db: db, src: src, drvr: d}, nil
}

// ValidateSource implements driver.Driver.
func (d *driveri) ValidateSource(src *source.Source) (*source.Source, error) {
	if src.Type != Type {
		return nil, errz.Errorf("expected source type %q but got %q", Type, src.Type)
	}
	return src, nil
}

// Ping implements driver.Driver.
func (d *driveri) Ping(ctx context.Context, src *source.Source) error {
	dbase, err := d.Open(context.TODO(), src)
	if err != nil {
		return err
	}
	defer d.log.WarnIfCloseError(dbase.DB())

	return dbase.DB().Ping()
}

// Truncate implements driver.SQLDriver. Arg reset is
// always ignored: the identity value is always reset by
// the TRUNCATE statement.
func (d *driveri) Truncate(ctx context.Context, src *source.Source, tbl string, reset bool) (affected int64, err error) {
	// https://dev.mysql.com/doc/refman/8.0/en/truncate-table.html
	dsn, err := dsnFromLocation(src)
	if err != nil {
		return 0, err
	}

	db, err := sql.Open(dbDrvr, dsn)
	if err != nil {
		return 0, errz.Err(err)
	}
	defer d.log.WarnIfFuncError(db.Close)

	// Not sure about the Tx requirements?
	tx, err := db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelSerializable})
	if err != nil {
		return 0, errz.Err(err)
	}

	// For whatever reason, the "affected" count from TRUNCATE
	// always returns zero. So, we're going to synthesize it.
	var beforeCount int64
	err = tx.QueryRowContext(ctx, fmt.Sprintf("SELECT COUNT(*) FROM `%s`", tbl)).Scan(&beforeCount)
	if err != nil {
		return 0, errz.Append(err, errz.Err(tx.Rollback()))
	}

	affected, err = sqlz.ExecResult(ctx, tx, fmt.Sprintf("TRUNCATE TABLE `%s`", tbl))
	if err != nil {
		return affected, errz.Append(err, errz.Err(tx.Rollback()))
	}

	if affected != 0 {
		// Note: At the time of writing, this doesn't happen:
		// zero is always returned (which we don't like).
		// If this changes (driver changes?) then we'll revisit.
		d.log.Warnf("Unexpectedly got non-zero (%d) rows affected from TRUNCATE", affected)
		return affected, errz.Err(tx.Commit())
	}

	// TRUNCATE succeeded, therefore tbl is empty, therefore
	// the count of truncated rows must be beforeCount?
	return beforeCount, errz.Err(tx.Commit())
}

// database implements driver.Database.
type database struct {
	log  lg.Log
	db   *sql.DB
	src  *source.Source
	drvr *driveri
}

// DB implements driver.Database.
func (d *database) DB() *sql.DB {
	return d.db
}

// SQLDriver implements driver.Database.
func (d *database) SQLDriver() driver.SQLDriver {
	return d.drvr
}

// Source implements driver.Database.
func (d *database) Source() *source.Source {
	return d.src
}

// TableMetadata implements driver.Database.
func (d *database) TableMetadata(ctx context.Context, tblName string) (*source.TableMetadata, error) {
	return getTableMetadata(ctx, d.log, d.db, tblName)
}

// SourceMetadata implements driver.Database.
func (d *database) SourceMetadata(ctx context.Context) (*source.Metadata, error) {
	return getSourceMetadata(ctx, d.log, d.src, d.db)
}

// Close implements driver.Database.
func (d *database) Close() error {
	d.log.Debugf("Close database: %s", d.src)
	return errz.Err(d.db.Close())
}

// hasErrCode returns true if err (or its cause error)
// is of type *mysql.MySQLError and err.Number equals code.
func hasErrCode(err error, code uint16) bool {
	err = errz.Cause(err)
	if err2, ok := err.(*mysql.MySQLError); ok {
		return err2.Number == code
	}
	return false
}

const errNumTableNotExist = uint16(1146)

// dsnFromLocation extracts the mysql driver DSN from src.Location.
func dsnFromLocation(src *source.Source) (string, error) {
	if !strings.HasPrefix(src.Location, "mysql://") || len(src.Location) < 10 {
		return "", errz.Errorf("invalid source location %s", src.RedactedLocation())
	}

	u, err := dburl.Parse(src.Location)
	if err != nil {
		return "", errz.Wrapf(err, "invalid source location %s", src.RedactedLocation())
	}

	// Convert the location to the desired driver DSN.
	// Location: 	mysql://sakila:p_ssW0rd@localhost:3306/sqtest
	// Driver DSN:	sakila:p_ssW0rd@tcp(localhost:3306)/sqtest
	driverDSN := fmt.Sprintf("%s@tcp(%s)%s", u.User.String(), u.Host, u.Path)

	_, err = mysql.ParseDSN(driverDSN) // verify
	if err != nil {
		return "", errz.Wrapf(err, "invalid source location: %q", driverDSN)
	}

	return driverDSN, nil
}