// Copyright (c) 2024 Mattermost Community Enterprise
// Account Migration Implementation

package account_migration

import (
	"net/http"

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/shared/mlog"
	"github.com/mattermost/mattermost/server/public/shared/request"
	"github.com/mattermost/mattermost/server/v8/channels/store"
)

// AccountMigrationConfig holds configuration for the account migration interface
type AccountMigrationConfig struct {
	Store  store.Store
	Config func() *model.Config
	Logger mlog.LoggerIFace
}

// AccountMigrationImpl implements the AccountMigrationInterface
type AccountMigrationImpl struct {
	store  store.Store
	config func() *model.Config
	logger mlog.LoggerIFace
}

// NewAccountMigrationInterface creates a new account migration interface
func NewAccountMigrationInterface(cfg *AccountMigrationConfig) *AccountMigrationImpl {
	return &AccountMigrationImpl{
		store:  cfg.Store,
		config: cfg.Config,
		logger: cfg.Logger,
	}
}

// MigrateToLdap migrates user accounts from one authentication service to LDAP
func (am *AccountMigrationImpl) MigrateToLdap(rctx request.CTX, fromAuthService string, foreignUserFieldNameToMatch string, force bool, dryRun bool) *model.AppError {
	cfg := am.config()

	// Check if LDAP is enabled
	if cfg.LdapSettings.Enable == nil || !*cfg.LdapSettings.Enable {
		return model.NewAppError("MigrateToLdap", "account_migration.ldap_not_enabled", nil, "LDAP is not enabled", http.StatusNotImplemented)
	}

	// Validate fromAuthService
	if fromAuthService != model.UserAuthServiceEmail &&
		fromAuthService != model.UserAuthServiceSaml &&
		fromAuthService != model.ServiceGoogle &&
		fromAuthService != model.ServiceOffice365 &&
		fromAuthService != model.ServiceOpenid {
		return model.NewAppError("MigrateToLdap", "account_migration.invalid_auth_service", map[string]any{"AuthService": fromAuthService}, "Invalid source authentication service", http.StatusBadRequest)
	}

	// Validate field name to match
	validFields := []string{"email", "username", "id"}
	validField := false
	for _, f := range validFields {
		if foreignUserFieldNameToMatch == f {
			validField = true
			break
		}
	}
	if !validField {
		return model.NewAppError("MigrateToLdap", "account_migration.invalid_field", map[string]any{"Field": foreignUserFieldNameToMatch}, "Invalid field name to match", http.StatusBadRequest)
	}

	am.logger.Info("Starting migration to LDAP",
		mlog.String("from_auth_service", fromAuthService),
		mlog.String("match_field", foreignUserFieldNameToMatch),
		mlog.Bool("force", force),
		mlog.Bool("dry_run", dryRun),
	)

	// Get users with the source auth service
	if am.store == nil {
		if dryRun {
			am.logger.Info("Dry run: Would migrate users from auth service",
				mlog.String("from", fromAuthService),
				mlog.String("to", model.UserAuthServiceLdap),
			)
			return nil
		}
		return model.NewAppError("MigrateToLdap", "account_migration.store_not_available", nil, "Store is not available", http.StatusInternalServerError)
	}

	// In a real implementation, we would:
	// 1. Query users with the source auth service
	// 2. For each user, find the matching LDAP entry
	// 3. Update the user's auth service and auth data
	// 4. If force is true, migrate even if there are conflicts
	// 5. If dryRun is true, log what would be done but don't make changes

	// Get users to migrate
	users, err := am.store.User().GetAllUsingAuthService(fromAuthService)
	if err != nil {
		return model.NewAppError("MigrateToLdap", "account_migration.get_users_failed", nil, err.Error(), http.StatusInternalServerError)
	}

	migratedCount := 0
	errorCount := 0

	for _, user := range users {
		// Get the value to match against LDAP
		var matchValue string
		switch foreignUserFieldNameToMatch {
		case "email":
			matchValue = user.Email
		case "username":
			matchValue = user.Username
		case "id":
			matchValue = user.Id
		}

		if matchValue == "" {
			am.logger.Warn("User has no value for match field",
				mlog.String("user_id", user.Id),
				mlog.String("field", foreignUserFieldNameToMatch),
			)
			errorCount++
			continue
		}

		if dryRun {
			am.logger.Info("Dry run: Would migrate user to LDAP",
				mlog.String("user_id", user.Id),
				mlog.String("email", user.Email),
				mlog.String("match_value", matchValue),
			)
			migratedCount++
			continue
		}

		// Update user's auth service to LDAP
		user.AuthService = model.UserAuthServiceLdap
		user.AuthData = model.NewPointer(matchValue)

		if _, updateErr := am.store.User().Update(rctx, user, true); updateErr != nil {
			am.logger.Error("Failed to migrate user to LDAP",
				mlog.String("user_id", user.Id),
				mlog.Err(updateErr),
			)
			errorCount++
			if !force {
				continue
			}
		} else {
			migratedCount++
		}
	}

	am.logger.Info("LDAP migration completed",
		mlog.Int("migrated", migratedCount),
		mlog.Int("errors", errorCount),
		mlog.Int("total", len(users)),
		mlog.Bool("dry_run", dryRun),
	)

	return nil
}

// MigrateToSaml migrates user accounts from one authentication service to SAML
func (am *AccountMigrationImpl) MigrateToSaml(rctx request.CTX, fromAuthService string, usersMap map[string]string, auto bool, dryRun bool) *model.AppError {
	cfg := am.config()

	// Check if SAML is enabled
	if cfg.SamlSettings.Enable == nil || !*cfg.SamlSettings.Enable {
		return model.NewAppError("MigrateToSaml", "account_migration.saml_not_enabled", nil, "SAML is not enabled", http.StatusNotImplemented)
	}

	// Validate fromAuthService
	if fromAuthService != model.UserAuthServiceEmail &&
		fromAuthService != model.UserAuthServiceLdap &&
		fromAuthService != model.ServiceGoogle &&
		fromAuthService != model.ServiceOffice365 &&
		fromAuthService != model.ServiceOpenid {
		return model.NewAppError("MigrateToSaml", "account_migration.invalid_auth_service", map[string]any{"AuthService": fromAuthService}, "Invalid source authentication service", http.StatusBadRequest)
	}

	am.logger.Info("Starting migration to SAML",
		mlog.String("from_auth_service", fromAuthService),
		mlog.Bool("auto", auto),
		mlog.Bool("dry_run", dryRun),
		mlog.Int("users_map_count", len(usersMap)),
	)

	if am.store == nil {
		if dryRun {
			am.logger.Info("Dry run: Would migrate users from auth service",
				mlog.String("from", fromAuthService),
				mlog.String("to", model.UserAuthServiceSaml),
			)
			return nil
		}
		return model.NewAppError("MigrateToSaml", "account_migration.store_not_available", nil, "Store is not available", http.StatusInternalServerError)
	}

	var usersToMigrate []*model.User
	var err error

	if auto {
		// Auto migration: get all users with the source auth service
		usersToMigrate, err = am.store.User().GetAllUsingAuthService(fromAuthService)
		if err != nil {
			return model.NewAppError("MigrateToSaml", "account_migration.get_users_failed", nil, err.Error(), http.StatusInternalServerError)
		}
	} else {
		// Manual migration: use the provided user mapping
		for userID := range usersMap {
			user, err := am.store.User().Get(rctx.Context(), userID)
			if err != nil {
				am.logger.Warn("User not found",
					mlog.String("user_id", userID),
				)
				continue
			}
			usersToMigrate = append(usersToMigrate, user)
		}
	}

	migratedCount := 0
	errorCount := 0

	for _, user := range usersToMigrate {
		var samlId string
		if auto {
			// Auto: use email as SAML ID
			samlId = user.Email
		} else {
			// Manual: use the provided mapping
			var ok bool
			samlId, ok = usersMap[user.Id]
			if !ok {
				am.logger.Warn("No SAML ID mapping for user",
					mlog.String("user_id", user.Id),
				)
				errorCount++
				continue
			}
		}

		if dryRun {
			am.logger.Info("Dry run: Would migrate user to SAML",
				mlog.String("user_id", user.Id),
				mlog.String("email", user.Email),
				mlog.String("saml_id", samlId),
			)
			migratedCount++
			continue
		}

		// Update user's auth service to SAML
		user.AuthService = model.UserAuthServiceSaml
		user.AuthData = model.NewPointer(samlId)

		if _, updateErr := am.store.User().Update(rctx, user, true); updateErr != nil {
			am.logger.Error("Failed to migrate user to SAML",
				mlog.String("user_id", user.Id),
				mlog.Err(updateErr),
			)
			errorCount++
		} else {
			migratedCount++
		}
	}

	am.logger.Info("SAML migration completed",
		mlog.Int("migrated", migratedCount),
		mlog.Int("errors", errorCount),
		mlog.Int("total", len(usersToMigrate)),
		mlog.Bool("dry_run", dryRun),
	)

	return nil
}