package classes

import (
	"context"
	"fmt"
	"log/slog"
	"strconv"
	"time"

	"git.golem15.com/golem15/sm-user-plugin/models"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
	"gocloud.dev/blob"
	"gorm.io/gorm"
)

// The functions in this file are the admin screen's user actions. Each takes
// the handle of the transaction the admin write runs in and never opens one
// of its own. None of them writes users_groups, except the cleanup of a user
// who is being deleted for good.

// ThrottleStates reads the ban and suspension state of userIDs from
// user_throttle in one query. A user is banned when any of their rows is
// banned, and suspended when a row is suspended and its suspended_at lies
// inside the suspension window (golem15.user.throttle.suspension_minutes,
// read from ctx as ContextWithThrottle stores it). It is a pure read: an
// expired suspension is not lifted here.
func ThrottleStates(ctx context.Context, db *gorm.DB, userIDs []uint) (banned, suspended map[uint]bool, err error) {
	banned, suspended = map[uint]bool{}, map[uint]bool{}
	if db == nil {
		return nil, nil, fmt.Errorf("golem15.user: gorm handle is missing")
	}
	if len(userIDs) == 0 {
		return banned, suspended, nil
	}
	minutes := throttleFrom(ctx).minutes
	if minutes <= 0 {
		minutes = 15
	}
	window := time.Duration(minutes) * time.Minute
	var rows []models.Throttle
	err = fresh(ctx, db).
		Where("user_id IN ? AND (is_banned OR is_suspended)", userIDs).
		Find(&rows).Error
	if err != nil {
		return nil, nil, err
	}
	now := time.Now()
	for _, row := range rows {
		if row.IsBanned {
			banned[row.UserID] = true
		}
		if row.IsSuspended && row.SuspendedAt != nil && now.Before(row.SuspendedAt.Add(window)) {
			suspended[row.UserID] = true
		}
	}
	return banned, suspended, nil
}

// ActivateUsers activates the users that are not active yet and returns how
// many it changed. Like VerifyActivationCode it sets is_activated, stamps
// activated_at, clears the activation code and restores a deactivated user.
// Users that are already active are skipped.
func ActivateUsers(ctx context.Context, db *gorm.DB, users []*models.User) (int, error) {
	if db == nil {
		return 0, fmt.Errorf("golem15.user: gorm handle is missing")
	}
	changed := 0
	for _, user := range users {
		if user == nil || user.ID == 0 || user.IsActivated {
			continue
		}
		now := time.Now()
		err := fresh(ctx, db).Unscoped().Model(&models.User{}).Where("id = ?", user.ID).UpdateColumns(map[string]any{
			"is_activated":              true,
			"activated_at":              now,
			"activation_code":           nil,
			"activation_code_issued_at": nil,
			"deleted_at":                nil,
		}).Error
		if err != nil {
			return 0, err
		}
		user.IsActivated = true
		user.ActivatedAt = &now
		user.ActivationCode = nil
		user.ActivationCodeIssuedAt = nil
		user.DeletedAt = gorm.DeletedAt{}
		changed++
	}
	return changed, nil
}

// DeactivateUsers soft-deletes the users that are not deactivated yet, the
// PHP $user->delete(), and returns how many it changed.
func DeactivateUsers(ctx context.Context, db *gorm.DB, users []*models.User) (int, error) {
	if db == nil {
		return 0, fmt.Errorf("golem15.user: gorm handle is missing")
	}
	changed := 0
	for _, user := range users {
		if user == nil || user.ID == 0 || user.DeletedAt.Valid {
			continue
		}
		now := time.Now()
		err := fresh(ctx, db).Unscoped().Model(&models.User{}).Where("id = ?", user.ID).UpdateColumn("deleted_at", now).Error
		if err != nil {
			return 0, err
		}
		user.DeletedAt = gorm.DeletedAt{Time: now, Valid: true}
		changed++
	}
	return changed, nil
}

// RestoreUsers brings deactivated users back, the PHP $user->restore(), and
// returns how many it changed.
func RestoreUsers(ctx context.Context, db *gorm.DB, users []*models.User) (int, error) {
	if db == nil {
		return 0, fmt.Errorf("golem15.user: gorm handle is missing")
	}
	changed := 0
	for _, user := range users {
		if user == nil || user.ID == 0 || !user.DeletedAt.Valid {
			continue
		}
		err := fresh(ctx, db).Unscoped().Model(&models.User{}).Where("id = ?", user.ID).UpdateColumn("deleted_at", nil).Error
		if err != nil {
			return 0, err
		}
		user.DeletedAt = gorm.DeletedAt{}
		changed++
	}
	return changed, nil
}

// BanUsers bans the users and returns how many were not banned before. A ban
// is set on every user_throttle row of the user, and a row without an IP
// address is created when the user has none, so a login from any address is
// refused (RejectIfThrottled falls back to that row).
func BanUsers(ctx context.Context, db *gorm.DB, users []*models.User) (int, error) {
	ids, err := userIDs(db, users)
	if err != nil {
		return 0, err
	}
	banned, _, err := ThrottleStates(ctx, db, ids)
	if err != nil {
		return 0, err
	}
	changed := 0
	for _, id := range ids {
		if err := fresh(ctx, db).Model(&models.Throttle{}).Where("user_id = ?", id).UpdateColumn("is_banned", true).Error; err != nil {
			return 0, err
		}
		var anyAddress int64
		if err := fresh(ctx, db).Model(&models.Throttle{}).Where("user_id = ? AND ip_address IS NULL", id).Count(&anyAddress).Error; err != nil {
			return 0, err
		}
		if anyAddress == 0 {
			if err := fresh(ctx, db).Create(&models.Throttle{UserID: id, IsBanned: true}).Error; err != nil {
				return 0, err
			}
		}
		if !banned[id] {
			changed++
		}
	}
	return changed, nil
}

// UnbanUsers clears the ban on every user_throttle row of the users and
// returns how many were banned before.
func UnbanUsers(ctx context.Context, db *gorm.DB, users []*models.User) (int, error) {
	ids, err := userIDs(db, users)
	if err != nil {
		return 0, err
	}
	banned, _, err := ThrottleStates(ctx, db, ids)
	if err != nil {
		return 0, err
	}
	changed := 0
	for _, id := range ids {
		if !banned[id] {
			continue
		}
		if err := fresh(ctx, db).Model(&models.Throttle{}).Where("user_id = ?", id).UpdateColumn("is_banned", false).Error; err != nil {
			return 0, err
		}
		changed++
	}
	return changed, nil
}

// UnsuspendUser lifts a suspension: it clears is_suspended, suspended_at and
// the attempt counter on every user_throttle row of the user.
func UnsuspendUser(ctx context.Context, db *gorm.DB, userID uint) error {
	if db == nil {
		return fmt.Errorf("golem15.user: gorm handle is missing")
	}
	return fresh(ctx, db).Model(&models.Throttle{}).Where("user_id = ?", userID).UpdateColumns(map[string]any{
		"is_suspended": false,
		"suspended_at": nil,
		"attempts":     0,
	}).Error
}

// ForceDeleteCleanup removes what hangs off a user who is being deleted for
// good: the user_throttle rows (their foreign key has no ON DELETE), the
// users_groups rows and the attachments. It runs inside the delete's
// transaction and does not delete the user row; the caller does that with
// the same handle. The attachments' blobs are removed only after the
// transaction commits, so a rollback leaves the files in place. bucket may be
// nil: the rows are still deleted.
func ForceDeleteCleanup(ctx context.Context, db *gorm.DB, bucket *blob.Bucket, user *models.User) error {
	if db == nil {
		return fmt.Errorf("golem15.user: gorm handle is missing")
	}
	if user == nil || user.ID == 0 {
		return fmt.Errorf("golem15.user: cannot clean up a user without an id")
	}
	if err := fresh(ctx, db).Exec(`DELETE FROM user_throttle WHERE user_id = ?`, user.ID).Error; err != nil {
		return err
	}
	if err := fresh(ctx, db).Exec(`DELETE FROM users_groups WHERE user_id = ?`, user.ID).Error; err != nil {
		return err
	}
	var keys []string
	err := attach.DeleteForOwner(fresh(ctx, db), user, strconv.FormatUint(uint64(user.ID), 10), func(blobKeys []string) error {
		keys = append(keys, blobKeys...)
		return nil
	})
	if err != nil {
		return err
	}
	if bucket == nil || len(keys) == 0 {
		return nil
	}
	userID := user.ID
	lagoon.AfterCommit(ctx, db, func(ctx context.Context, _ *gorm.DB) {
		// The rows are gone by now, so a blob that cannot be removed is
		// orphaned, not lost data: log it and carry on.
		if err := attach.DeleteKeys(ctx, bucket, keys); err != nil {
			slog.Default().Warn("golem15.user: remove attachment blobs of a deleted user", "user_id", userID, "err", err)
		}
	})
	return nil
}

// fresh returns db with an empty statement on ctx, so a query never continues
// from conditions the caller's handle already carries. A NewDB session is
// lazy: GORM builds the empty statement on the next chain method, and a
// WithContext chained directly onto it clones the caller's statement with its
// conditions instead. Clauses() makes the empty statement exist first, so the
// handle stays clean whatever is chained next.
func fresh(ctx context.Context, db *gorm.DB) *gorm.DB {
	return db.Session(&gorm.Session{NewDB: true, Context: ctx}).Clauses().Session(&gorm.Session{NewDB: true})
}

// userIDs returns the ids of users, skipping nil and unsaved entries.
func userIDs(db *gorm.DB, users []*models.User) ([]uint, error) {
	if db == nil {
		return nil, fmt.Errorf("golem15.user: gorm handle is missing")
	}
	ids := make([]uint, 0, len(users))
	for _, user := range users {
		if user != nil && user.ID != 0 {
			ids = append(ids, user.ID)
		}
	}
	return ids, nil
}