// Copyright 2019 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.

package syncer

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

	"github.com/go-sql-driver/mysql"
	"github.com/pingcap/errors"
	"github.com/pingcap/failpoint"
	"github.com/pingcap/tidb/pkg/errno"
	"github.com/pingcap/tidb/pkg/infoschema"
	"github.com/pingcap/tidb/pkg/meta/model"
	"github.com/pingcap/tidb/pkg/parser"
	"github.com/pingcap/tidb/pkg/parser/ast"
	tmysql "github.com/pingcap/tidb/pkg/parser/mysql"
	"github.com/pingcap/tidb/pkg/util/dbterror"
	"github.com/pingcap/tidb/pkg/util/dbutil"
	tcontext "github.com/pingcap/tiflow/dm/pkg/context"
	"github.com/pingcap/tiflow/dm/pkg/log"
	"github.com/pingcap/tiflow/dm/pkg/terror"
	"github.com/pingcap/tiflow/dm/syncer/dbconn"
	"github.com/pingcap/tiflow/pkg/errorutil"
	"go.uber.org/zap"
)

// ignoreTrackerDDLError is also same with ignoreDDLError, but in order to keep tracker's table structure same as
// upstream's, we can't ignore "already exists" errors because already exists doesn't mean same.
func ignoreTrackerDDLError(err error) bool {
	switch {
	case infoschema.ErrDatabaseExists.Equal(err), infoschema.ErrDatabaseDropExists.Equal(err),
		infoschema.ErrTableDropExists.Equal(err),
		dbterror.ErrCantDropFieldOrKey.Equal(err):
		return true
	default:
		return false
	}
}

func isDropColumnWithIndexError(err error) bool {
	mysqlErr, ok := errors.Cause(err).(*mysql.MySQLError)
	if !ok {
		return false
	}
	// different version of TiDB has different error message, try to cover most versions
	return (mysqlErr.Number == errno.ErrUnsupportedDDLOperation || mysqlErr.Number == tmysql.ErrUnknown) &&
		strings.Contains(mysqlErr.Message, "drop column") &&
		(strings.Contains(mysqlErr.Message, "with index") ||
			strings.Contains(mysqlErr.Message, "with composite index") ||
			strings.Contains(mysqlErr.Message, "with tidb_enable_change_multi_schema is disable"))
}

// handleSpecialDDLError handles special errors for DDL execution
// if createTime equals to -1, skip the handle procedure for waitAsyncDDL.
func (s *Syncer) handleSpecialDDLError(tctx *tcontext.Context, err error, ddls []string, index int, conn *dbconn.DBConn, createTime int64) error {
	// We use default parser because ddls are came from *Syncer.genDDLInfo, which is StringSingleQuotes, KeyWordUppercase and NameBackQuotes
	parser2 := parser.New()

	// it only ignore `invalid connection` error (timeout or other causes) for `ADD INDEX`.
	// `invalid connection` means some data already sent to the server,
	// and we assume that the whole SQL statement has already sent to the server for this error.
	// if we have other methods to judge the DDL dispatched but timeout for executing, we can update this method.
	// NOTE: we must ensure other PK/UK exists for correctness.
	// NOTE: when we are refactoring the shard DDL algorithm, we also need to consider supporting non-blocking `ADD INDEX`.
	ignoreAddIndexTimeout := func(tctx *tcontext.Context, err error, ddls []string, index int, conn *dbconn.DBConn, createTime int64) error {
		// must ensure only the last statement executed failed with the `invalid connection` error
		if len(ddls) == 0 || index != len(ddls)-1 || errors.Cause(err) != mysql.ErrInvalidConn {
			return err // return the original error
		}

		ddl2 := ddls[index]
		stmt, err2 := parser2.ParseOneStmt(ddl2, "", "")
		if err2 != nil {
			return err // return the original error
		}

		handle := func() {
			tctx.L().Warn("ignore special error for DDL", zap.String("DDL", ddl2), log.ShortError(err))
			err2 := conn.ResetConn(tctx) // also reset the `invalid connection` for later use.
			if err2 != nil {
				tctx.L().Warn("reset connection failed", log.ShortError(err2))
			}
		}

		switch v := stmt.(type) {
		case *ast.AlterTableStmt:
			// ddls should be split with only one spec
			if len(v.Specs) > 1 {
				return err
			} else if v.Specs[0].Tp == ast.AlterTableAddConstraint {
				// only take effect on `ADD INDEX`, no UNIQUE KEY and FOREIGN KEY
				// UNIQUE KEY may affect correctness, FOREIGN KEY should be filtered.
				// ref https://github.com/pingcap/tidb/blob/3cdea0dfdf28197ee65545debce8c99e6d2945e3/ddl/ddl_api.go#L1929-L1948.
				switch v.Specs[0].Constraint.Tp {
				case ast.ConstraintKey, ast.ConstraintIndex:
					handle()
					return nil // ignore the error
				}
			}
		case *ast.CreateIndexStmt:
			handle()
			return nil // ignore the error
		}
		return err
	}

	// for DROP COLUMN with its single-column index, try drop index first then drop column
	// TiDB will support DROP COLUMN with index soon. After its support, executing that SQL will not have an error,
	// so this function will not trigger and cause some trouble
	dropColumnF := func(tctx *tcontext.Context, originErr error, ddls []string, index int, conn *dbconn.DBConn, createTime int64) error {
		if !isDropColumnWithIndexError(originErr) {
			return originErr
		}
		ddl2 := ddls[index]
		stmt, err2 := parser2.ParseOneStmt(ddl2, "", "")
		if err2 != nil {
			return originErr // return the original error
		}

		var (
			schema string
			table  string
			col    string
		)
		n, ok := stmt.(*ast.AlterTableStmt)
		switch {
		case !ok:
			return originErr
		case len(n.Specs) != 1:
			return originErr
		case n.Specs[0].Tp != ast.AlterTableDropColumn:
			return originErr
		default:
			schema = n.Table.Schema.O
			table = n.Table.Name.O
			col = n.Specs[0].OldColumnName.Name.O
		}
		tctx.L().Warn("try to fix drop column error", zap.String("DDL", ddl2), log.ShortError(originErr))

		// check if dependent index is single-column index on this column
		sql2 := "SELECT INDEX_NAME FROM information_schema.statistics WHERE TABLE_SCHEMA = ? and TABLE_NAME = ? and COLUMN_NAME = ?"
		var rows *sql.Rows
		rows, err2 = conn.QuerySQL(tctx, s.metricsProxies, sql2, schema, table, col)
		if err2 != nil {
			return originErr
		}
		var (
			idx       string
			idx2Check []string
			idx2Drop  []string
			count     int
		)
		for rows.Next() {
			if err2 = rows.Scan(&idx); err2 != nil {
				// nolint:sqlclosecheck
				rows.Close()
				return originErr
			}
			idx2Check = append(idx2Check, idx)
		}
		if rows.Err() != nil {
			return rows.Err()
		}
		// Close is idempotent, we could close in advance to reuse conn
		rows.Close()

		sql2 = "SELECT count(*) FROM information_schema.statistics WHERE TABLE_SCHEMA = ? and TABLE_NAME = ? and INDEX_NAME = ?"
		for _, idx := range idx2Check {
			rows, err2 = conn.QuerySQL(tctx, s.metricsProxies, sql2, schema, table, idx)
			if err2 != nil || !rows.Next() || rows.Scan(&count) != nil || count != 1 {
				tctx.L().Warn("can't auto drop index", zap.String("index", idx))
				if rows != nil {
					// nolint: sqlclosecheck
					rows.Close()
				}
				return originErr
			}
			if rows.Err() != nil {
				return rows.Err()
			}
			idx2Drop = append(idx2Drop, idx)
			rows.Close()
		}

		sqls := make([]string, len(idx2Drop))
		for i, idx := range idx2Drop {
			sqls[i] = fmt.Sprintf("ALTER TABLE %s DROP INDEX %s", dbutil.TableName(schema, table), dbutil.ColumnName(idx))
		}
		if _, err2 = conn.ExecuteSQL(tctx, s.metricsProxies, sqls); err2 != nil {
			tctx.L().Warn("auto drop index failed", log.ShortError(err2))
			return originErr
		}

		tctx.L().Info("drop index success, now try to drop column", zap.Strings("index", idx2Drop))
		if _, err2 = conn.ExecuteSQLWithIgnore(tctx, s.metricsProxies, errorutil.IsIgnorableMySQLDDLError, ddls[index:]); err2 != nil {
			return err2
		}

		tctx.L().Info("execute drop column SQL success", zap.String("DDL", ddl2))
		return nil
	}
	// TODO: add support for downstream alter pk without schema

	// it handles the operations for DDL when encountering `invalid connection` by waiting the asynchronous ddl to synchronize
	waitAsyncDDL := func(tctx *tcontext.Context, err error, ddls []string, index int, conn *dbconn.DBConn, createTime int64) error {
		if len(ddls) == 0 || index > len(ddls)-1 || errors.Cause(err) != mysql.ErrInvalidConn || createTime == -1 {
			return err // return the original error
		}

		duration := 30
		failpoint.Inject("ChangeDuration", func() {
			duration = 1
		})
		ticker := time.NewTicker(time.Duration(duration) * time.Second)
		defer ticker.Stop()

		for {
			status, err2 := getDDLStatusFromTiDB(tctx, conn, ddls[index], createTime)
			if err2 != nil {
				s.tctx.L().Warn("error when getting DDL status from TiDB", zap.Error(err2))
			}
			failpoint.Inject("TestStatus", func(val failpoint.Value) {
				status = val.(string)
				s.tctx.L().Info("injected test status:", zap.String("TestStatus", status))
			})
			switch status {
			case model.JobStateDone.String(), model.JobStateSynced.String():
				return nil
			case model.JobStateCancelled.String(), model.JobStateRollingback.String(), model.JobStateRollbackDone.String(), model.JobStateCancelling.String():
				return terror.ErrSyncerCancelledDDL.Generate(ddls[index])
			case model.JobStateRunning.String(), model.JobStateQueueing.String(), model.JobStateNone.String():
			default:
				tctx.L().Warn("Unexpected DDL status", zap.String("DDL status", status))
				return err
			}
			select {
			case <-tctx.Ctx.Done():
				return err
			case <-ticker.C:
			}
		}
	}

	retErr := err
	toHandle := []func(*tcontext.Context, error, []string, int, *dbconn.DBConn, int64) error{
		dropColumnF,
		ignoreAddIndexTimeout,
		waitAsyncDDL,
	}
	for _, f := range toHandle {
		retErr = f(tctx, retErr, ddls, index, conn, createTime)
		if retErr == nil {
			break
		}
	}
	return retErr
}

func isDuplicateServerIDError(err error) bool {
	if err == nil {
		return false
	}

	return strings.Contains(err.Error(), "A slave with the same server_uuid/server_id as this slave has connected to the master")
}

func isConnectionRefusedError(err error) bool {
	if err == nil {
		return false
	}

	return strings.Contains(err.Error(), "connect: connection refused")
}