package data

import (
	"fmt"
	"strings"
	"time"

	"gorm.io/gorm"
)

func migrateAll(db *gorm.DB) error {
	if err := migrateLegacyIgnoreAPITable(db); err != nil {
		return err
	}
	if err := migrateLegacyAuthorityDepartmentColumns(db); err != nil {
		return err
	}
	if err := db.AutoMigrate(
		&userPO{}, &authorityPO{}, &menuPO{}, &userAuthorityPO{}, &authorityMenuPO{}, &menuParameterPO{},
		&apiPO{}, &ignoredAPIPO{}, &authorityAPIPO{}, &casbinRulePO{}, &menuButtonPO{}, &authorityButtonPO{},
		&departmentPO{}, &positionPO{}, &userDepartmentPO{}, &userPositionPO{}, &authorityDepartmentPO{},
		&dictionaryPO{}, &dictionaryDetailPO{}, &parameterPO{}, &apiTokenPO{}, &jwtBlacklistPO{}, &securityConfigPO{},
		&versionPO{}, &exportTemplatePO{}, &exportConditionPO{}, &exportJoinPO{},
		&operationPO{}, &loginLogPO{}, &dataAccessLogPO{}, &errorRecordPO{},
		&taskPO{}, &taskLogPO{}, &mediaPO{}, &categoryPO{}, &uploadSessionPO{}, &uploadChunkPO{},
		&announcementPO{},
	); err != nil {
		return err
	}
	if err := migrateLegacyAuthorityAPIsToCasbinRules(db); err != nil {
		return err
	}
	if err := normalizeErrorRecordStatuses(db); err != nil {
		return err
	}
	if err := reconcileRootAuthorityAPIs(db); err != nil {
		return err
	}
	return reconcileReferenceIndexes(db)
}

// migrateLegacyAuthorityDepartmentColumns preserves data created by early
// Kra builds, which used shortened join-column names and a composite primary
// key. The administration connection model has neither a primary key nor a
// uniqueness constraint, so rebuild the small table before AutoMigrate.
func migrateLegacyAuthorityDepartmentColumns(db *gorm.DB) error {
	clean := db.Session(&gorm.Session{NewDB: true})
	const (
		table  = "sys_authority_departments"
		backup = "sys_authority_departments_kra_legacy"
	)
	// MySQL and Oracle auto-commit DDL. If a prior process stopped between the
	// rename and cleanup steps, restore the untouched backup first and retry the
	// migration from a known state.
	if clean.Migrator().HasTable(backup) {
		if clean.Migrator().HasTable(table) {
			if err := clean.Migrator().DropTable(table); err != nil {
				return fmt.Errorf("remove incomplete authority-department table: %w", err)
			}
		}
		if err := clean.Migrator().RenameTable(backup, table); err != nil {
			return fmt.Errorf("restore authority-department backup: %w", err)
		}
	}
	if !clean.Migrator().HasTable(table) {
		return nil
	}

	authorityColumn := "sys_authority_authority_id"
	if !tableHasColumn(clean, table, authorityColumn) {
		if !tableHasColumn(clean, table, "authority_id") {
			return fmt.Errorf("authority-department table has no authority column")
		}
		authorityColumn = "authority_id"
	}
	departmentColumn := "sys_department_id"
	if !tableHasColumn(clean, table, departmentColumn) {
		if !tableHasColumn(clean, table, "department_id") {
			return fmt.Errorf("authority-department table has no department column")
		}
		departmentColumn = "department_id"
	}
	hasPrimaryKey, err := tableHasPrimaryKey(clean, table)
	if err != nil {
		return err
	}
	if authorityColumn == "sys_authority_authority_id" && departmentColumn == "sys_department_id" && !hasPrimaryKey {
		return nil
	}

	type relation struct {
		AuthorityID  uint `gorm:"column:authority_id"`
		DepartmentID uint `gorm:"column:department_id"`
	}
	var rows []relation
	selectColumns := authorityColumn + " AS authority_id, " + departmentColumn + " AS department_id"
	if err := clean.Table(table).Select(selectColumns).Scan(&rows).Error; err != nil {
		return fmt.Errorf("read legacy authority-department rows: %w", err)
	}

	rebuild := func(tx *gorm.DB) error {
		if err := tx.Migrator().RenameTable(table, backup); err != nil {
			return fmt.Errorf("rename legacy authority-department table: %w", err)
		}
		if err := tx.AutoMigrate(&authorityDepartmentPO{}); err != nil {
			return fmt.Errorf("create authority-department table: %w", err)
		}
		if len(rows) > 0 {
			items := make([]authorityDepartmentPO, 0, len(rows))
			for _, row := range rows {
				items = append(items, authorityDepartmentPO{AuthorityID: row.AuthorityID, DepartmentID: row.DepartmentID})
			}
			if err := tx.Create(&items).Error; err != nil {
				return fmt.Errorf("copy authority-department rows: %w", err)
			}
		}
		var count int64
		if err := tx.Model(&authorityDepartmentPO{}).Count(&count).Error; err != nil {
			return fmt.Errorf("verify authority-department rows: %w", err)
		}
		if count != int64(len(rows)) {
			return fmt.Errorf("verify authority-department rows: got %d want %d", count, len(rows))
		}
		if err := tx.Migrator().DropTable(backup); err != nil {
			return fmt.Errorf("drop legacy authority-department table: %w", err)
		}
		return nil
	}

	switch clean.Dialector.Name() {
	case "mysql", "oracle":
		if err := rebuild(clean); err != nil {
			restoreErr := restoreAuthorityDepartmentBackup(clean, table, backup)
			if restoreErr != nil {
				return fmt.Errorf("%v; restore authority-department backup: %w", err, restoreErr)
			}
			return err
		}
		return nil
	default:
		return clean.Transaction(rebuild)
	}
}

func restoreAuthorityDepartmentBackup(db *gorm.DB, table, backup string) error {
	if db.Migrator().HasTable(table) {
		if err := db.Migrator().DropTable(table); err != nil {
			return err
		}
	}
	if db.Migrator().HasTable(backup) {
		return db.Migrator().RenameTable(backup, table)
	}
	return nil
}

func tableHasPrimaryKey(db *gorm.DB, table string) (bool, error) {
	columns, err := db.Migrator().ColumnTypes(table)
	if err != nil {
		return false, err
	}
	for _, column := range columns {
		if primary, ok := column.PrimaryKey(); ok && primary {
			return true, nil
		}
	}
	return false, nil
}

// Older builds used a status label outside the administration page's supported
// state set, so normalize existing rows during migration.
func normalizeErrorRecordStatuses(db *gorm.DB) error {
	return db.Session(&gorm.Session{NewDB: true}).Model(&errorRecordPO{}).Where("status = ?", "未解决").Update("status", "未处理").Error
}

// migrateLegacyAuthorityAPIsToCasbinRules upgrades the early Kra join-table
// representation to the independent Casbin policy table. Keep the legacy
// table in place for backwards compatibility, but make casbin_rule the sole
// live policy source. Existing policy rows are not duplicated.
func migrateLegacyAuthorityAPIsToCasbinRules(db *gorm.DB) error {
	clean := db.Session(&gorm.Session{NewDB: true})
	if !clean.Migrator().HasTable(&authorityAPIPO{}) || !clean.Migrator().HasTable(&casbinRulePO{}) {
		return nil
	}
	type legacyPolicy struct {
		AuthorityID uint
		Path        string
		Method      string
	}
	baseQuery := func() *gorm.DB {
		return clean.Table("sys_authority_apis sa").
			Select("sa.authority_id, a.path, a.method").
			Joins("JOIN sys_apis a ON a.id = sa.api_id")
	}
	query := baseQuery()
	// Early Kra schemas stored sys_apis without soft-delete timestamps. The
	// legacy-policy migration must run before assuming that column exists;
	// otherwise an upgrade from those schemas cannot start on MySQL.
	if tableHasColumn(clean, "sys_apis", "deleted_at") {
		query = query.Where("a.deleted_at IS NULL")
	}
	var rows []legacyPolicy
	if err := query.Find(&rows).Error; err != nil {
		// A few MySQL-compatible drivers report stale/incomplete metadata from
		// INFORMATION_SCHEMA during startup. If the optional soft-delete column
		// was reported present but the join still rejects it, retry using only
		// columns shared by every legacy schema. This migration must never block
		// startup of an older database solely because deleted_at is absent.
		if strings.Contains(strings.ToLower(err.Error()), "unknown column") && strings.Contains(strings.ToLower(err.Error()), "deleted_at") {
			if retryErr := baseQuery().Find(&rows).Error; retryErr != nil {
				return retryErr
			}
		} else {
			return err
		}
	}
	for _, row := range rows {
		exists, err := policyExists(clean, row.AuthorityID, row.Path, row.Method)
		if err != nil {
			return err
		}
		if exists {
			continue
		}
		if err := clean.Create(&casbinRulePO{Ptype: "p", V0: fmt.Sprint(row.AuthorityID), V1: row.Path, V2: row.Method}).Error; err != nil {
			return err
		}
	}
	return nil
}

// tableHasColumn deliberately inspects the physical table rather than the
// model schema. Legacy databases may predate soft-delete columns even though
// the current PO includes gorm.DeletedAt. Metadata inspection failures are
// treated as "unknown" so callers use the portable query shape.
func tableHasColumn(db *gorm.DB, table, column string) bool {
	columns, err := db.Migrator().ColumnTypes(table)
	if err != nil {
		return false
	}
	for _, item := range columns {
		if strings.EqualFold(item.Name(), column) {
			return true
		}
	}
	return false
}

// migrateLegacyIgnoreAPITable upgrades the early Kra-only composite-key
// shape (path, method) to the compatible model shape (ID/timestamps/soft
// delete).  AutoMigrate can add columns but cannot replace an existing
// composite primary key portably, so rebuild the small table once while
// preserving every existing ignore rule.
func migrateLegacyIgnoreAPITable(db *gorm.DB) error {
	clean := db.Session(&gorm.Session{NewDB: true})
	if !clean.Migrator().HasTable(&ignoredAPIPO{}) || clean.Migrator().HasColumn(&ignoredAPIPO{}, "id") {
		return nil
	}
	legacyTable := fmt.Sprintf("sys_ignore_apis_legacy_%d", time.Now().UnixNano())
	type legacyIgnoredAPI struct {
		Path   string
		Method string
	}
	return clean.Transaction(func(tx *gorm.DB) error {
		if err := tx.Migrator().RenameTable(ignoredAPIPO{}.TableName(), legacyTable); err != nil {
			return fmt.Errorf("rename legacy ignore API table: %w", err)
		}
		if err := tx.AutoMigrate(&ignoredAPIPO{}); err != nil {
			return fmt.Errorf("create compatible ignore API table: %w", err)
		}
		var rows []legacyIgnoredAPI
		if err := tx.Table(legacyTable).Find(&rows).Error; err != nil {
			return fmt.Errorf("read legacy ignore API rows: %w", err)
		}
		if len(rows) > 0 {
			items := make([]ignoredAPIPO, 0, len(rows))
			for _, row := range rows {
				items = append(items, ignoredAPIPO{Path: row.Path, Method: row.Method})
			}
			if err := tx.Create(&items).Error; err != nil {
				return fmt.Errorf("copy legacy ignore API rows: %w", err)
			}
		}
		if err := tx.Migrator().DropTable(legacyTable); err != nil {
			return fmt.Errorf("drop legacy ignore API table: %w", err)
		}
		return nil
	})
}

// reconcileRootAuthorityAPIs is a one-time upgrade path from the former Kra
// implementation where authority 888 bypassed policy storage entirely. The compatible behavior
// grants its root role through persisted Casbin policies, so when a legacy
// database has the root role but no stored API links, materialize the same
// policy set and let normal authorization read it thereafter.
func reconcileRootAuthorityAPIs(db *gorm.DB) error {
	clean := db.Session(&gorm.Session{NewDB: true})
	var authorityCount int64
	if err := clean.Session(&gorm.Session{NewDB: true}).Model(&authorityPO{}).Where("authority_id = ?", 888).Count(&authorityCount).Error; err != nil || authorityCount == 0 {
		return err
	}
	var policyCount int64
	if err := policyScope(clean).Where("v0 = ?", "888").Count(&policyCount).Error; err != nil || policyCount != 0 {
		return err
	}
	var ignored []ignoredAPIPO
	if err := clean.Session(&gorm.Session{NewDB: true}).Find(&ignored).Error; err != nil {
		return err
	}
	ignoreSet := make(map[string]struct{}, len(ignored))
	for _, item := range ignored {
		ignoreSet[item.Method+"\x00"+item.Path] = struct{}{}
	}
	var apis []apiPO
	if err := clean.Session(&gorm.Session{NewDB: true}).Find(&apis).Error; err != nil {
		return err
	}
	rules := make([]casbinRulePO, 0, len(apis))
	for _, api := range apis {
		if _, ok := ignoreSet[api.Method+"\x00"+api.Path]; ok {
			continue
		}
		rules = append(rules, newPolicyRule(888, api.Path, api.Method))
	}
	if len(rules) == 0 {
		return nil
	}
	return clean.Session(&gorm.Session{NewDB: true}).Create(&rules).Error
}

// reconcileReferenceIndexes removes constraints created by older Kra builds
// that are not part of the administration data model. Business services own
// duplicate checks and their user-facing error messages.
func reconcileReferenceIndexes(db *gorm.DB) error {
	clean := db.Session(&gorm.Session{NewDB: true})
	obsolete := []struct {
		model any
		name  string
	}{
		{&apiPO{}, "idx_api_path_method"},
		{&dictionaryPO{}, "idx_sys_dictionaries_type"},
		{&parameterPO{}, "idx_sys_params_key"},
		{&apiTokenPO{}, "idx_sys_api_tokens_token"},
		{&exportTemplatePO{}, "idx_sys_export_templates_template_id"},
	}
	for _, item := range obsolete {
		migrator := clean.Session(&gorm.Session{NewDB: true}).Migrator()
		if migrator.HasIndex(item.model, item.name) {
			if err := migrator.DropIndex(item.model, item.name); err != nil {
				return fmt.Errorf("drop obsolete index %s: %w", item.name, err)
			}
		}
	}
	for _, item := range []struct {
		name  string
		field string
	}{{"idx_sys_users_uuid", "UUID"}, {"idx_sys_users_username", "Username"}} {
		unique, err := indexIsUnique(clean.Session(&gorm.Session{NewDB: true}), &userPO{}, item.name)
		if err != nil {
			return err
		}
		if !unique {
			continue
		}
		migrator := clean.Session(&gorm.Session{NewDB: true}).Migrator()
		if err = migrator.DropIndex(&userPO{}, item.name); err != nil {
			return fmt.Errorf("drop legacy unique index %s: %w", item.name, err)
		}
		if err = migrator.CreateIndex(&userPO{}, item.field); err != nil {
			return fmt.Errorf("create reference index %s: %w", item.name, err)
		}
	}
	return nil
}

func indexIsUnique(db *gorm.DB, model any, name string) (bool, error) {
	indexes, err := db.Migrator().GetIndexes(model)
	if err != nil {
		// Some third-party GORM drivers do not implement index inspection.
		// Fresh schemas are already correct; skip only the legacy repair there.
		return false, nil
	}
	for _, index := range indexes {
		if index.Name() == name {
			unique, known := index.Unique()
			return known && unique, nil
		}
	}
	return false, nil
}