// Copyright 2015 The Gogs Authors. All rights reserved.
// Copyright 2017 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package migrations

import (
	"context"
	"errors"
	"fmt"
	"os"
	"reflect"
	"regexp"
	"strings"

	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/setting"

	"xorm.io/xorm"
	"xorm.io/xorm/names"
	"xorm.io/xorm/schemas"
)

const minDBVersion = 70 // Gitea 1.5.3

// Migration describes on migration from lower version to high version
type Migration interface {
	Description() string
	Migrate(*xorm.Engine) error
}

type migration struct {
	description string
	migrate     func(*xorm.Engine) error
}

// NewMigration creates a new migration
func NewMigration(desc string, fn func(*xorm.Engine) error) Migration {
	return &migration{desc, fn}
}

// Description returns the migration's description
func (m *migration) Description() string {
	return m.description
}

// Migrate executes the migration
func (m *migration) Migrate(x *xorm.Engine) error {
	return m.migrate(x)
}

// Version describes the version table. Should have only one row with id==1
type Version struct {
	ID      int64 `xorm:"pk autoincr"`
	Version int64
}

// This is a sequence of migrations. Add new migrations to the bottom of the list.
// If you want to "retire" a migration, remove it from the top of the list and
// update minDBVersion accordingly
var migrations = []Migration{
	// Gitea 1.5.0 ends at v69
	// v70 -> v71
	NewMigration("add issue_dependencies", addIssueDependencies),
	// v71 -> v72
	NewMigration("protect each scratch token", addScratchHash),
	// v72 -> v73
	NewMigration("add review", addReview),

	// Gitea 1.6.0 ends at v73

	// v73 -> v74
	NewMigration("add must_change_password column for users table", addMustChangePassword),
	// v74 -> v75
	NewMigration("add approval whitelists to protected branches", addApprovalWhitelistsToProtectedBranches),
	// v75 -> v76
	NewMigration("clear nonused data which not deleted when user was deleted", clearNonusedData),

	// Gitea 1.7.0 ends at v76

	// v76 -> v77
	NewMigration("add pull request rebase with merge commit", addPullRequestRebaseWithMerge),
	// v77 -> v78
	NewMigration("add theme to users", addUserDefaultTheme),
	// v78 -> v79
	NewMigration("rename repo is_bare to repo is_empty", renameRepoIsBareToIsEmpty),
	// v79 -> v80
	NewMigration("add can close issues via commit in any branch", addCanCloseIssuesViaCommitInAnyBranch),
	// v80 -> v81
	NewMigration("add is locked to issues", addIsLockedToIssues),
	// v81 -> v82
	NewMigration("update U2F counter type", changeU2FCounterType),

	// Gitea 1.8.0 ends at v82

	// v82 -> v83
	NewMigration("hot fix for wrong release sha1 on release table", fixReleaseSha1OnReleaseTable),
	// v83 -> v84
	NewMigration("add uploader id for table attachment", addUploaderIDForAttachment),
	// v84 -> v85
	NewMigration("add table to store original imported gpg keys", addGPGKeyImport),
	// v85 -> v86
	NewMigration("hash application token", hashAppToken),
	// v86 -> v87
	NewMigration("add http method to webhook", addHTTPMethodToWebhook),
	// v87 -> v88
	NewMigration("add avatar field to repository", addAvatarFieldToRepository),

	// Gitea 1.9.0 ends at v88

	// v88 -> v89
	NewMigration("add commit status context field to commit_status", addCommitStatusContext),
	// v89 -> v90
	NewMigration("add original author/url migration info to issues, comments, and repo ", addOriginalMigrationInfo),
	// v90 -> v91
	NewMigration("change length of some repository columns", changeSomeColumnsLengthOfRepo),
	// v91 -> v92
	NewMigration("add index on owner_id of repository and type, review_id of comment", addIndexOnRepositoryAndComment),
	// v92 -> v93
	NewMigration("remove orphaned repository index statuses", removeLingeringIndexStatus),
	// v93 -> v94
	NewMigration("add email notification enabled preference to user", addEmailNotificationEnabledToUser),
	// v94 -> v95
	NewMigration("add enable_status_check, status_check_contexts to protected_branch", addStatusCheckColumnsForProtectedBranches),
	// v95 -> v96
	NewMigration("add table columns for cross referencing issues", addCrossReferenceColumns),
	// v96 -> v97
	NewMigration("delete orphaned attachments", deleteOrphanedAttachments),
	// v97 -> v98
	NewMigration("add repo_admin_change_team_access to user", addRepoAdminChangeTeamAccessColumnForUser),
	// v98 -> v99
	NewMigration("add original author name and id on migrated release", addOriginalAuthorOnMigratedReleases),
	// v99 -> v100
	NewMigration("add task table and status column for repository table", addTaskTable),
	// v100 -> v101
	NewMigration("update migration repositories' service type", updateMigrationServiceTypes),
	// v101 -> v102
	NewMigration("change length of some external login users columns", changeSomeColumnsLengthOfExternalLoginUser),

	// Gitea 1.10.0 ends at v102

	// v102 -> v103
	NewMigration("update migration repositories' service type", dropColumnHeadUserNameOnPullRequest),
	// v103 -> v104
	NewMigration("Add WhitelistDeployKeys to protected branch", addWhitelistDeployKeysToBranches),
	// v104 -> v105
	NewMigration("remove unnecessary columns from label", removeLabelUneededCols),
	// v105 -> v106
	NewMigration("add includes_all_repositories to teams", addTeamIncludesAllRepositories),
	// v106 -> v107
	NewMigration("add column `mode` to table watch", addModeColumnToWatch),
	// v107 -> v108
	NewMigration("Add template options to repository", addTemplateToRepo),
	// v108 -> v109
	NewMigration("Add comment_id on table notification", addCommentIDOnNotification),
	// v109 -> v110
	NewMigration("add can_create_org_repo to team", addCanCreateOrgRepoColumnForTeam),
	// v110 -> v111
	NewMigration("change review content type to text", changeReviewContentToText),
	// v111 -> v112
	NewMigration("update branch protection for can push and whitelist enable", addBranchProtectionCanPushAndEnableWhitelist),
	// v112 -> v113
	NewMigration("remove release attachments which repository deleted", removeAttachmentMissedRepo),
	// v113 -> v114
	NewMigration("new feature: change target branch of pull requests", featureChangeTargetBranch),
	// v114 -> v115
	NewMigration("Remove authentication credentials from stored URL", sanitizeOriginalURL),
	// v115 -> v116
	NewMigration("add user_id prefix to existing user avatar name", renameExistingUserAvatarName),
	// v116 -> v117
	NewMigration("Extend TrackedTimes", extendTrackedTimes),

	// Gitea 1.11.0 ends at v117

	// v117 -> v118
	NewMigration("Add block on rejected reviews branch protection", addBlockOnRejectedReviews),
	// v118 -> v119
	NewMigration("Add commit id and stale to reviews", addReviewCommitAndStale),
	// v119 -> v120
	NewMigration("Fix migrated repositories' git service type", fixMigratedRepositoryServiceType),
	// v120 -> v121
	NewMigration("Add owner_name on table repository", addOwnerNameOnRepository),
	// v121 -> v122
	NewMigration("add is_restricted column for users table", addIsRestricted),
	// v122 -> v123
	NewMigration("Add Require Signed Commits to ProtectedBranch", addRequireSignedCommits),
	// v123 -> v124
	NewMigration("Add original information for reactions", addReactionOriginals),
	// v124 -> v125
	NewMigration("Add columns to user and repository", addUserRepoMissingColumns),
	// v125 -> v126
	NewMigration("Add some columns on review for migration", addReviewMigrateInfo),
	// v126 -> v127
	NewMigration("Fix topic repository count", fixTopicRepositoryCount),
	// v127 -> v128
	NewMigration("add repository code language statistics", addLanguageStats),
	// v128 -> v129
	NewMigration("fix merge base for pull requests", fixMergeBase),
	// v129 -> v130
	NewMigration("remove dependencies from deleted repositories", purgeUnusedDependencies),
	// v130 -> v131
	NewMigration("Expand webhooks for more granularity", expandWebhooks),
	// v131 -> v132
	NewMigration("Add IsSystemWebhook column to webhooks table", addSystemWebhookColumn),
	// v132 -> v133
	NewMigration("Add Branch Protection Protected Files Column", addBranchProtectionProtectedFilesColumn),
	// v133 -> v134
	NewMigration("Add EmailHash Table", addEmailHashTable),
	// v134 -> v135
	NewMigration("Refix merge base for merged pull requests", refixMergeBase),
	// v135 -> v136
	NewMigration("Add OrgID column to Labels table", addOrgIDLabelColumn),
	// v136 -> v137
	NewMigration("Add CommitsAhead and CommitsBehind Column to PullRequest Table", addCommitDivergenceToPulls),
	// v137 -> v138
	NewMigration("Add Branch Protection Block Outdated Branch", addBlockOnOutdatedBranch),
	// v138 -> v139
	NewMigration("Add ResolveDoerID to Comment table", addResolveDoerIDCommentColumn),
	// v139 -> v140
	NewMigration("prepend refs/heads/ to issue refs", prependRefsHeadsToIssueRefs),

	// Gitea 1.12.0 ends at v140

	// v140 -> v141
	NewMigration("Save detected language file size to database instead of percent", fixLanguageStatsToSaveSize),
	// v141 -> v142
	NewMigration("Add KeepActivityPrivate to User table", addKeepActivityPrivateUserColumn),
	// v142 -> v143
	NewMigration("Ensure Repository.IsArchived is not null", setIsArchivedToFalse),
	// v143 -> v144
	NewMigration("recalculate Stars number for all user", recalculateStars),
	// v144 -> v145
	NewMigration("update Matrix Webhook http method to 'PUT'", updateMatrixWebhookHTTPMethod),
	// v145 -> v146
	NewMigration("Increase Language field to 50 in LanguageStats", increaseLanguageField),
	// v146 -> v147
	NewMigration("Add projects info to repository table", addProjectsInfo),
	// v147 -> v148
	NewMigration("create review for 0 review id code comments", createReviewsForCodeComments),
	// v148 -> v149
	NewMigration("remove issue dependency comments who refer to non existing issues", purgeInvalidDependenciesComments),
	// v149 -> v150
	NewMigration("Add Created and Updated to Milestone table", addCreatedAndUpdatedToMilestones),
	// v150 -> v151
	NewMigration("add primary key to repo_topic", addPrimaryKeyToRepoTopic),
	// v151 -> v152
	NewMigration("set default password algorithm to Argon2", setDefaultPasswordToArgon2),
	// v152 -> v153
	NewMigration("add TrustModel field to Repository", addTrustModelToRepository),
	// v153 > v154
	NewMigration("add Team review request support", addTeamReviewRequestSupport),
	// v154 > v155
	NewMigration("add timestamps to Star, Label, Follow, Watch and Collaboration", addTimeStamps),

	// Gitea 1.13.0 ends at v155

	// v155 -> v156
	NewMigration("add changed_protected_files column for pull_request table", addChangedProtectedFilesPullRequestColumn),
	// v156 -> v157
	NewMigration("fix publisher ID for tag releases", fixPublisherIDforTagReleases),
	// v157 -> v158
	NewMigration("ensure repo topics are up-to-date", fixRepoTopics),
	// v158 -> v159
	NewMigration("code comment replies should have the commitID of the review they are replying to", updateCodeCommentReplies),
	// v159 -> v160
	NewMigration("update reactions constraint", updateReactionConstraint),
	// v160 -> v161
	NewMigration("Add block on official review requests branch protection", addBlockOnOfficialReviewRequests),
	// v161 -> v162
	NewMigration("Convert task type from int to string", convertTaskTypeToString),
	// v162 -> v163
	NewMigration("Convert webhook task type from int to string", convertWebhookTaskTypeToString),
	// v163 -> v164
	NewMigration("Convert topic name from 25 to 50", convertTopicNameFrom25To50),
	// v164 -> v165
	NewMigration("Add scope and nonce columns to oauth2_grant table", addScopeAndNonceColumnsToOAuth2Grant),
	// v165 -> v166
	NewMigration("Convert hook task type from char(16) to varchar(16) and trim the column", convertHookTaskTypeToVarcharAndTrim),
	// v166 -> v167
	NewMigration("Where Password is Valid with Empty String delete it", recalculateUserEmptyPWD),
	// v167 -> v168
	NewMigration("Add user redirect", addUserRedirect),
	// v168 -> v169
	NewMigration("Recreate user table to fix default values", recreateUserTableToFixDefaultValues),
	// v169 -> v170
	NewMigration("Update DeleteBranch comments to set the old_ref to the commit_sha", commentTypeDeleteBranchUseOldRef),
	// v170 -> v171
	NewMigration("Add Dismissed to Review table", addDismissedReviewColumn),
	// v171 -> v172
	NewMigration("Add Sorting to ProjectBoard table", addSortingColToProjectBoard),
	// v172 -> v173
	NewMigration("Add sessions table for go-chi/session", addSessionTable),
	// v173 -> v174
	NewMigration("Add time_id column to Comment", addTimeIDCommentColumn),
	// v174 -> v175
	NewMigration("Create repo transfer table", addRepoTransfer),
	// v175 -> v176
	NewMigration("Fix Postgres ID Sequences broken by recreate-table", fixPostgresIDSequences),
	// v176 -> v177
	NewMigration("Remove invalid labels from comments", removeInvalidLabels),
	// v177 -> v178
	NewMigration("Delete orphaned IssueLabels", deleteOrphanedIssueLabels),

	// Gitea 1.14.0 ends at v178

	// v178 -> v179
	NewMigration("Add LFS columns to Mirror", addLFSMirrorColumns),
	// v179 -> v180
	NewMigration("Convert avatar url to text", convertAvatarURLToText),
	// v180 -> v181
	NewMigration("Delete credentials from past migrations", deleteMigrationCredentials),
	// v181 -> v182
	NewMigration("Always save primary email on email address table", addPrimaryEmail2EmailAddress),
	// v182 -> v183
	NewMigration("Add issue resource index table", addIssueResourceIndexTable),
	// v183 -> v184
	NewMigration("Create PushMirror table", createPushMirrorTable),
	// v184 -> v185
	NewMigration("Rename Task errors to message", renameTaskErrorsToMessage),
	// v185 -> v186
	NewMigration("Add new table repo_archiver", addRepoArchiver),
	// v186 -> v187
	NewMigration("Create protected tag table", createProtectedTagTable),
	// v187 -> v188
	NewMigration("Drop unneeded webhook related columns", dropWebhookColumns),
	// v188 -> v189
	NewMigration("Add key is verified to gpg key", addKeyIsVerified),

	// Gitea 1.15.0 ends at v189

	// v189 -> v190
	NewMigration("Unwrap ldap.Sources", unwrapLDAPSourceCfg),
	// v190 -> v191
	NewMigration("Add agit flow pull request support", addAgitFlowPullRequest),
	// v191 -> v192
	NewMigration("Alter issue/comment table TEXT fields to LONGTEXT", alterIssueAndCommentTextFieldsToLongText),
	// v192 -> v193
	NewMigration("RecreateIssueResourceIndexTable to have a primary key instead of an unique index", recreateIssueResourceIndexTable),
	// v193 -> v194
	NewMigration("Add repo id column for attachment table", addRepoIDForAttachment),
	// v194 -> v195
	NewMigration("Add Branch Protection Unprotected Files Column", addBranchProtectionUnprotectedFilesColumn),
	// v195 -> v196
	NewMigration("Add table commit_status_index", addTableCommitStatusIndex),
	// v196 -> v197
	NewMigration("Add Color to ProjectBoard table", addColorColToProjectBoard),
	// v197 -> v198
	NewMigration("Add renamed_branch table", addRenamedBranchTable),
	// v198 -> v199
	NewMigration("Add issue content history table", addTableIssueContentHistory),
	// v199 -> v200
	NewMigration("No-op (remote version is using AppState now)", addRemoteVersionTableNoop),
	// v200 -> v201
	NewMigration("Add table app_state", addTableAppState),
	// v201 -> v202
	NewMigration("Drop table remote_version (if exists)", dropTableRemoteVersion),
	// v202 -> v203
	NewMigration("Create key/value table for user settings", createUserSettingsTable),
	// v203 -> v204
	NewMigration("Add Sorting to ProjectIssue table", addProjectIssueSorting),
	// v204 -> v205
	NewMigration("Add key is verified to ssh key", addSSHKeyIsVerified),
	// v205 -> v206
	NewMigration("Migrate to higher varchar on user struct", migrateUserPasswordSalt),
	// v206 -> v207
	NewMigration("Add authorize column to team_unit table", addAuthorizeColForTeamUnit),
	// v207 -> v208
	NewMigration("Add webauthn table and migrate u2f data to webauthn - NO-OPED", addWebAuthnCred),
	// v208 -> v209
	NewMigration("Use base32.HexEncoding instead of base64 encoding for cred ID as it is case insensitive - NO-OPED", useBase32HexForCredIDInWebAuthnCredential),
	// v209 -> v210
	NewMigration("Increase WebAuthentication CredentialID size to 410 - NO-OPED", increaseCredentialIDTo410),
	// v210 -> v211
	NewMigration("v208 was completely broken - remigrate", remigrateU2FCredentials),
}

// GetCurrentDBVersion returns the current db version
func GetCurrentDBVersion(x *xorm.Engine) (int64, error) {
	if err := x.Sync(new(Version)); err != nil {
		return -1, fmt.Errorf("sync: %v", err)
	}

	currentVersion := &Version{ID: 1}
	has, err := x.Get(currentVersion)
	if err != nil {
		return -1, fmt.Errorf("get: %v", err)
	}
	if !has {
		return -1, nil
	}
	return currentVersion.Version, nil
}

// ExpectedVersion returns the expected db version
func ExpectedVersion() int64 {
	return int64(minDBVersion + len(migrations))
}

// EnsureUpToDate will check if the db is at the correct version
func EnsureUpToDate(x *xorm.Engine) error {
	currentDB, err := GetCurrentDBVersion(x)
	if err != nil {
		return err
	}

	if currentDB < 0 {
		return fmt.Errorf("Database has not been initialised")
	}

	if minDBVersion > currentDB {
		return fmt.Errorf("DB version %d (<= %d) is too old for auto-migration. Upgrade to Gitea 1.6.4 first then upgrade to this version", currentDB, minDBVersion)
	}

	expected := ExpectedVersion()

	if currentDB != expected {
		return fmt.Errorf(`Current database version %d is not equal to the expected version %d. Please run "gitea [--config /path/to/app.ini] migrate" to update the database version`, currentDB, expected)
	}

	return nil
}

// Migrate database to current version
func Migrate(x *xorm.Engine) error {
	// Set a new clean the default mapper to GonicMapper as that is the default for Gitea.
	x.SetMapper(names.GonicMapper{})
	if err := x.Sync(new(Version)); err != nil {
		return fmt.Errorf("sync: %v", err)
	}

	currentVersion := &Version{ID: 1}
	has, err := x.Get(currentVersion)
	if err != nil {
		return fmt.Errorf("get: %v", err)
	} else if !has {
		// If the version record does not exist we think
		// it is a fresh installation and we can skip all migrations.
		currentVersion.ID = 0
		currentVersion.Version = int64(minDBVersion + len(migrations))

		if _, err = x.InsertOne(currentVersion); err != nil {
			return fmt.Errorf("insert: %v", err)
		}
	}

	v := currentVersion.Version
	if minDBVersion > v {
		log.Fatal(`Gitea no longer supports auto-migration from your previously installed version.
Please try upgrading to a lower version first (suggested v1.6.4), then upgrade to this version.`)
		return nil
	}

	// Downgrading Gitea's database version not supported
	if int(v-minDBVersion) > len(migrations) {
		msg := fmt.Sprintf("Your database (migration version: %d) is for a newer Gitea, you can not use the newer database for this old Gitea release (%d).", v, minDBVersion+len(migrations))
		msg += "\nGitea will exit to keep your database safe and unchanged. Please use the correct Gitea release, do not change the migration version manually (incorrect manual operation may lose data)."
		if !setting.IsProd {
			msg += fmt.Sprintf("\nIf you are in development and really know what you're doing, you can force changing the migration version by executing: UPDATE version SET version=%d WHERE id=1;", minDBVersion+len(migrations))
		}
		_, _ = fmt.Fprintln(os.Stderr, msg)
		log.Fatal(msg)
		return nil
	}

	// Migrate
	for i, m := range migrations[v-minDBVersion:] {
		log.Info("Migration[%d]: %s", v+int64(i), m.Description())
		// Reset the mapper between each migration - migrations are not supposed to depend on each other
		x.SetMapper(names.GonicMapper{})
		if err = m.Migrate(x); err != nil {
			return fmt.Errorf("migration[%d]: %s failed: %v", v+int64(i), m.Description(), err)
		}
		currentVersion.Version = v + int64(i) + 1
		if _, err = x.ID(1).Update(currentVersion); err != nil {
			return err
		}
	}
	return nil
}

// RecreateTables will recreate the tables for the provided beans using the newly provided bean definition and move all data to that new table
// WARNING: YOU MUST PROVIDE THE FULL BEAN DEFINITION
func RecreateTables(beans ...interface{}) func(*xorm.Engine) error {
	return func(x *xorm.Engine) error {
		sess := x.NewSession()
		defer sess.Close()
		if err := sess.Begin(); err != nil {
			return err
		}
		sess = sess.StoreEngine("InnoDB")
		for _, bean := range beans {
			log.Info("Recreating Table: %s for Bean: %s", x.TableName(bean), reflect.Indirect(reflect.ValueOf(bean)).Type().Name())
			if err := recreateTable(sess, bean); err != nil {
				return err
			}
		}
		return sess.Commit()
	}
}

// recreateTable will recreate the table using the newly provided bean definition and move all data to that new table
// WARNING: YOU MUST PROVIDE THE FULL BEAN DEFINITION
// WARNING: YOU MUST COMMIT THE SESSION AT THE END
func recreateTable(sess *xorm.Session, bean interface{}) error {
	// TODO: This will not work if there are foreign keys

	tableName := sess.Engine().TableName(bean)
	tempTableName := fmt.Sprintf("tmp_recreate__%s", tableName)

	// We need to move the old table away and create a new one with the correct columns
	// We will need to do this in stages to prevent data loss
	//
	// First create the temporary table
	if err := sess.Table(tempTableName).CreateTable(bean); err != nil {
		log.Error("Unable to create table %s. Error: %v", tempTableName, err)
		return err
	}

	if err := sess.Table(tempTableName).CreateUniques(bean); err != nil {
		log.Error("Unable to create uniques for table %s. Error: %v", tempTableName, err)
		return err
	}

	if err := sess.Table(tempTableName).CreateIndexes(bean); err != nil {
		log.Error("Unable to create indexes for table %s. Error: %v", tempTableName, err)
		return err
	}

	// Work out the column names from the bean - these are the columns to select from the old table and install into the new table
	table, err := sess.Engine().TableInfo(bean)
	if err != nil {
		log.Error("Unable to get table info. Error: %v", err)

		return err
	}
	newTableColumns := table.Columns()
	if len(newTableColumns) == 0 {
		return fmt.Errorf("no columns in new table")
	}
	hasID := false
	for _, column := range newTableColumns {
		hasID = hasID || (column.IsPrimaryKey && column.IsAutoIncrement)
	}

	if hasID && setting.Database.UseMSSQL {
		if _, err := sess.Exec(fmt.Sprintf("SET IDENTITY_INSERT `%s` ON", tempTableName)); err != nil {
			log.Error("Unable to set identity insert for table %s. Error: %v", tempTableName, err)
			return err
		}
	}

	sqlStringBuilder := &strings.Builder{}
	_, _ = sqlStringBuilder.WriteString("INSERT INTO `")
	_, _ = sqlStringBuilder.WriteString(tempTableName)
	_, _ = sqlStringBuilder.WriteString("` (`")
	_, _ = sqlStringBuilder.WriteString(newTableColumns[0].Name)
	_, _ = sqlStringBuilder.WriteString("`")
	for _, column := range newTableColumns[1:] {
		_, _ = sqlStringBuilder.WriteString(", `")
		_, _ = sqlStringBuilder.WriteString(column.Name)
		_, _ = sqlStringBuilder.WriteString("`")
	}
	_, _ = sqlStringBuilder.WriteString(")")
	_, _ = sqlStringBuilder.WriteString(" SELECT ")
	if newTableColumns[0].Default != "" {
		_, _ = sqlStringBuilder.WriteString("COALESCE(`")
		_, _ = sqlStringBuilder.WriteString(newTableColumns[0].Name)
		_, _ = sqlStringBuilder.WriteString("`, ")
		_, _ = sqlStringBuilder.WriteString(newTableColumns[0].Default)
		_, _ = sqlStringBuilder.WriteString(")")
	} else {
		_, _ = sqlStringBuilder.WriteString("`")
		_, _ = sqlStringBuilder.WriteString(newTableColumns[0].Name)
		_, _ = sqlStringBuilder.WriteString("`")
	}

	for _, column := range newTableColumns[1:] {
		if column.Default != "" {
			_, _ = sqlStringBuilder.WriteString(", COALESCE(`")
			_, _ = sqlStringBuilder.WriteString(column.Name)
			_, _ = sqlStringBuilder.WriteString("`, ")
			_, _ = sqlStringBuilder.WriteString(column.Default)
			_, _ = sqlStringBuilder.WriteString(")")
		} else {
			_, _ = sqlStringBuilder.WriteString(", `")
			_, _ = sqlStringBuilder.WriteString(column.Name)
			_, _ = sqlStringBuilder.WriteString("`")
		}
	}
	_, _ = sqlStringBuilder.WriteString(" FROM `")
	_, _ = sqlStringBuilder.WriteString(tableName)
	_, _ = sqlStringBuilder.WriteString("`")

	if _, err := sess.Exec(sqlStringBuilder.String()); err != nil {
		log.Error("Unable to set copy data in to temp table %s. Error: %v", tempTableName, err)
		return err
	}

	if hasID && setting.Database.UseMSSQL {
		if _, err := sess.Exec(fmt.Sprintf("SET IDENTITY_INSERT `%s` OFF", tempTableName)); err != nil {
			log.Error("Unable to switch off identity insert for table %s. Error: %v", tempTableName, err)
			return err
		}
	}

	switch {
	case setting.Database.UseSQLite3:
		// SQLite will drop all the constraints on the old table
		if _, err := sess.Exec(fmt.Sprintf("DROP TABLE `%s`", tableName)); err != nil {
			log.Error("Unable to drop old table %s. Error: %v", tableName, err)
			return err
		}

		if err := sess.Table(tempTableName).DropIndexes(bean); err != nil {
			log.Error("Unable to drop indexes on temporary table %s. Error: %v", tempTableName, err)
			return err
		}

		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` RENAME TO `%s`", tempTableName, tableName)); err != nil {
			log.Error("Unable to rename %s to %s. Error: %v", tempTableName, tableName, err)
			return err
		}

		if err := sess.Table(tableName).CreateIndexes(bean); err != nil {
			log.Error("Unable to recreate indexes on table %s. Error: %v", tableName, err)
			return err
		}

		if err := sess.Table(tableName).CreateUniques(bean); err != nil {
			log.Error("Unable to recreate uniques on table %s. Error: %v", tableName, err)
			return err
		}

	case setting.Database.UseMySQL:
		// MySQL will drop all the constraints on the old table
		if _, err := sess.Exec(fmt.Sprintf("DROP TABLE `%s`", tableName)); err != nil {
			log.Error("Unable to drop old table %s. Error: %v", tableName, err)
			return err
		}

		if err := sess.Table(tempTableName).DropIndexes(bean); err != nil {
			log.Error("Unable to drop indexes on temporary table %s. Error: %v", tempTableName, err)
			return err
		}

		// SQLite and MySQL will move all the constraints from the temporary table to the new table
		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` RENAME TO `%s`", tempTableName, tableName)); err != nil {
			log.Error("Unable to rename %s to %s. Error: %v", tempTableName, tableName, err)
			return err
		}

		if err := sess.Table(tableName).CreateIndexes(bean); err != nil {
			log.Error("Unable to recreate indexes on table %s. Error: %v", tableName, err)
			return err
		}

		if err := sess.Table(tableName).CreateUniques(bean); err != nil {
			log.Error("Unable to recreate uniques on table %s. Error: %v", tableName, err)
			return err
		}
	case setting.Database.UsePostgreSQL:
		var originalSequences []string
		type sequenceData struct {
			LastValue int  `xorm:"'last_value'"`
			IsCalled  bool `xorm:"'is_called'"`
		}
		sequenceMap := map[string]sequenceData{}

		schema := sess.Engine().Dialect().URI().Schema
		sess.Engine().SetSchema("")
		if err := sess.Table("information_schema.sequences").Cols("sequence_name").Where("sequence_name LIKE ? || '_%' AND sequence_catalog = ?", tableName, setting.Database.Name).Find(&originalSequences); err != nil {
			log.Error("Unable to rename %s to %s. Error: %v", tempTableName, tableName, err)
			return err
		}
		sess.Engine().SetSchema(schema)

		for _, sequence := range originalSequences {
			sequenceData := sequenceData{}
			if _, err := sess.Table(sequence).Cols("last_value", "is_called").Get(&sequenceData); err != nil {
				log.Error("Unable to get last_value and is_called from %s. Error: %v", sequence, err)
				return err
			}
			sequenceMap[sequence] = sequenceData

		}

		// CASCADE causes postgres to drop all the constraints on the old table
		if _, err := sess.Exec(fmt.Sprintf("DROP TABLE `%s` CASCADE", tableName)); err != nil {
			log.Error("Unable to drop old table %s. Error: %v", tableName, err)
			return err
		}

		// CASCADE causes postgres to move all the constraints from the temporary table to the new table
		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` RENAME TO `%s`", tempTableName, tableName)); err != nil {
			log.Error("Unable to rename %s to %s. Error: %v", tempTableName, tableName, err)
			return err
		}

		var indices []string
		sess.Engine().SetSchema("")
		if err := sess.Table("pg_indexes").Cols("indexname").Where("tablename = ? ", tableName).Find(&indices); err != nil {
			log.Error("Unable to rename %s to %s. Error: %v", tempTableName, tableName, err)
			return err
		}
		sess.Engine().SetSchema(schema)

		for _, index := range indices {
			newIndexName := strings.Replace(index, "tmp_recreate__", "", 1)
			if _, err := sess.Exec(fmt.Sprintf("ALTER INDEX `%s` RENAME TO `%s`", index, newIndexName)); err != nil {
				log.Error("Unable to rename %s to %s. Error: %v", index, newIndexName, err)
				return err
			}
		}

		var sequences []string
		sess.Engine().SetSchema("")
		if err := sess.Table("information_schema.sequences").Cols("sequence_name").Where("sequence_name LIKE 'tmp_recreate__' || ? || '_%' AND sequence_catalog = ?", tableName, setting.Database.Name).Find(&sequences); err != nil {
			log.Error("Unable to rename %s to %s. Error: %v", tempTableName, tableName, err)
			return err
		}
		sess.Engine().SetSchema(schema)

		for _, sequence := range sequences {
			newSequenceName := strings.Replace(sequence, "tmp_recreate__", "", 1)
			if _, err := sess.Exec(fmt.Sprintf("ALTER SEQUENCE `%s` RENAME TO `%s`", sequence, newSequenceName)); err != nil {
				log.Error("Unable to rename %s sequence to %s. Error: %v", sequence, newSequenceName, err)
				return err
			}
			val, ok := sequenceMap[newSequenceName]
			if newSequenceName == tableName+"_id_seq" {
				if ok && val.LastValue != 0 {
					if _, err := sess.Exec(fmt.Sprintf("SELECT setval('%s', %d, %t)", newSequenceName, val.LastValue, val.IsCalled)); err != nil {
						log.Error("Unable to reset %s to %d. Error: %v", newSequenceName, val, err)
						return err
					}
				} else {
					// We're going to try to guess this
					if _, err := sess.Exec(fmt.Sprintf("SELECT setval('%s', COALESCE((SELECT MAX(id)+1 FROM `%s`), 1), false)", newSequenceName, tableName)); err != nil {
						log.Error("Unable to reset %s. Error: %v", newSequenceName, err)
						return err
					}
				}
			} else if ok {
				if _, err := sess.Exec(fmt.Sprintf("SELECT setval('%s', %d, %t)", newSequenceName, val.LastValue, val.IsCalled)); err != nil {
					log.Error("Unable to reset %s to %d. Error: %v", newSequenceName, val, err)
					return err
				}
			}

		}

	case setting.Database.UseMSSQL:
		// MSSQL will drop all the constraints on the old table
		if _, err := sess.Exec(fmt.Sprintf("DROP TABLE `%s`", tableName)); err != nil {
			log.Error("Unable to drop old table %s. Error: %v", tableName, err)
			return err
		}

		// MSSQL sp_rename will move all the constraints from the temporary table to the new table
		if _, err := sess.Exec(fmt.Sprintf("sp_rename `%s`,`%s`", tempTableName, tableName)); err != nil {
			log.Error("Unable to rename %s to %s. Error: %v", tempTableName, tableName, err)
			return err
		}

	default:
		log.Fatal("Unrecognized DB")
	}
	return nil
}

// WARNING: YOU MUST COMMIT THE SESSION AT THE END
func dropTableColumns(sess *xorm.Session, tableName string, columnNames ...string) (err error) {
	if tableName == "" || len(columnNames) == 0 {
		return nil
	}
	// TODO: This will not work if there are foreign keys

	switch {
	case setting.Database.UseSQLite3:
		// First drop the indexes on the columns
		res, errIndex := sess.Query(fmt.Sprintf("PRAGMA index_list(`%s`)", tableName))
		if errIndex != nil {
			return errIndex
		}
		for _, row := range res {
			indexName := row["name"]
			indexRes, err := sess.Query(fmt.Sprintf("PRAGMA index_info(`%s`)", indexName))
			if err != nil {
				return err
			}
			if len(indexRes) != 1 {
				continue
			}
			indexColumn := string(indexRes[0]["name"])
			for _, name := range columnNames {
				if name == indexColumn {
					_, err := sess.Exec(fmt.Sprintf("DROP INDEX `%s`", indexName))
					if err != nil {
						return err
					}
				}
			}
		}

		// Here we need to get the columns from the original table
		sql := fmt.Sprintf("SELECT sql FROM sqlite_master WHERE tbl_name='%s' and type='table'", tableName)
		res, err := sess.Query(sql)
		if err != nil {
			return err
		}
		tableSQL := string(res[0]["sql"])

		// Get the string offset for column definitions: `CREATE TABLE ( column-definitions... )`
		columnDefinitionsIndex := strings.Index(tableSQL, "(")
		if columnDefinitionsIndex < 0 {
			return errors.New("couldn't find column definitions")
		}

		// Separate out the column definitions
		tableSQL = tableSQL[columnDefinitionsIndex:]

		// Remove the required columnNames
		for _, name := range columnNames {
			tableSQL = regexp.MustCompile(regexp.QuoteMeta("`"+name+"`")+"[^`,)]*?[,)]").ReplaceAllString(tableSQL, "")
		}

		// Ensure the query is ended properly
		tableSQL = strings.TrimSpace(tableSQL)
		if tableSQL[len(tableSQL)-1] != ')' {
			if tableSQL[len(tableSQL)-1] == ',' {
				tableSQL = tableSQL[:len(tableSQL)-1]
			}
			tableSQL += ")"
		}

		// Find all the columns in the table
		columns := regexp.MustCompile("`([^`]*)`").FindAllString(tableSQL, -1)

		tableSQL = fmt.Sprintf("CREATE TABLE `new_%s_new` ", tableName) + tableSQL
		if _, err := sess.Exec(tableSQL); err != nil {
			return err
		}

		// Now restore the data
		columnsSeparated := strings.Join(columns, ",")
		insertSQL := fmt.Sprintf("INSERT INTO `new_%s_new` (%s) SELECT %s FROM %s", tableName, columnsSeparated, columnsSeparated, tableName)
		if _, err := sess.Exec(insertSQL); err != nil {
			return err
		}

		// Now drop the old table
		if _, err := sess.Exec(fmt.Sprintf("DROP TABLE `%s`", tableName)); err != nil {
			return err
		}

		// Rename the table
		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `new_%s_new` RENAME TO `%s`", tableName, tableName)); err != nil {
			return err
		}

	case setting.Database.UsePostgreSQL:
		cols := ""
		for _, col := range columnNames {
			if cols != "" {
				cols += ", "
			}
			cols += "DROP COLUMN `" + col + "` CASCADE"
		}
		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` %s", tableName, cols)); err != nil {
			return fmt.Errorf("Drop table `%s` columns %v: %v", tableName, columnNames, err)
		}
	case setting.Database.UseMySQL:
		// Drop indexes on columns first
		sql := fmt.Sprintf("SHOW INDEX FROM %s WHERE column_name IN ('%s')", tableName, strings.Join(columnNames, "','"))
		res, err := sess.Query(sql)
		if err != nil {
			return err
		}
		for _, index := range res {
			indexName := index["column_name"]
			if len(indexName) > 0 {
				_, err := sess.Exec(fmt.Sprintf("DROP INDEX `%s` ON `%s`", indexName, tableName))
				if err != nil {
					return err
				}
			}
		}

		// Now drop the columns
		cols := ""
		for _, col := range columnNames {
			if cols != "" {
				cols += ", "
			}
			cols += "DROP COLUMN `" + col + "`"
		}
		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` %s", tableName, cols)); err != nil {
			return fmt.Errorf("Drop table `%s` columns %v: %v", tableName, columnNames, err)
		}
	case setting.Database.UseMSSQL:
		cols := ""
		for _, col := range columnNames {
			if cols != "" {
				cols += ", "
			}
			cols += "`" + strings.ToLower(col) + "`"
		}
		sql := fmt.Sprintf("SELECT Name FROM sys.default_constraints WHERE parent_object_id = OBJECT_ID('%[1]s') AND parent_column_id IN (SELECT column_id FROM sys.columns WHERE LOWER(name) IN (%[2]s) AND object_id = OBJECT_ID('%[1]s'))",
			tableName, strings.ReplaceAll(cols, "`", "'"))
		constraints := make([]string, 0)
		if err := sess.SQL(sql).Find(&constraints); err != nil {
			return fmt.Errorf("Find constraints: %v", err)
		}
		for _, constraint := range constraints {
			if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` DROP CONSTRAINT `%s`", tableName, constraint)); err != nil {
				return fmt.Errorf("Drop table `%s` default constraint `%s`: %v", tableName, constraint, err)
			}
		}
		sql = fmt.Sprintf("SELECT DISTINCT Name FROM sys.indexes INNER JOIN sys.index_columns ON indexes.index_id = index_columns.index_id AND indexes.object_id = index_columns.object_id WHERE indexes.object_id = OBJECT_ID('%[1]s') AND index_columns.column_id IN (SELECT column_id FROM sys.columns WHERE LOWER(name) IN (%[2]s) AND object_id = OBJECT_ID('%[1]s'))",
			tableName, strings.ReplaceAll(cols, "`", "'"))
		constraints = make([]string, 0)
		if err := sess.SQL(sql).Find(&constraints); err != nil {
			return fmt.Errorf("Find constraints: %v", err)
		}
		for _, constraint := range constraints {
			if _, err := sess.Exec(fmt.Sprintf("DROP INDEX `%[2]s` ON `%[1]s`", tableName, constraint)); err != nil {
				return fmt.Errorf("Drop index `%[2]s` on `%[1]s`: %v", tableName, constraint, err)
			}
		}

		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` DROP COLUMN %s", tableName, cols)); err != nil {
			return fmt.Errorf("Drop table `%s` columns %v: %v", tableName, columnNames, err)
		}
	default:
		log.Fatal("Unrecognized DB")
	}

	return nil
}

// modifyColumn will modify column's type or other propertity. SQLITE is not supported
func modifyColumn(x *xorm.Engine, tableName string, col *schemas.Column) error {
	var indexes map[string]*schemas.Index
	var err error
	// MSSQL have to remove index at first, otherwise alter column will fail
	// ref. https://sqlzealots.com/2018/05/09/error-message-the-index-is-dependent-on-column-alter-table-alter-column-failed-because-one-or-more-objects-access-this-column/
	if x.Dialect().URI().DBType == schemas.MSSQL {
		indexes, err = x.Dialect().GetIndexes(x.DB(), context.Background(), tableName)
		if err != nil {
			return err
		}

		for _, index := range indexes {
			_, err = x.Exec(x.Dialect().DropIndexSQL(tableName, index))
			if err != nil {
				return err
			}
		}
	}

	defer func() {
		for _, index := range indexes {
			_, err = x.Exec(x.Dialect().CreateIndexSQL(tableName, index))
			if err != nil {
				log.Error("Create index %s on table %s failed: %v", index.Name, tableName, err)
			}
		}
	}()

	alterSQL := x.Dialect().ModifyColumnSQL(tableName, col)
	if _, err := x.Exec(alterSQL); err != nil {
		return err
	}
	return nil
}
