package user

import (
	"context"
	"errors"

	"git.golem15.com/golem15/sm-user-plugin/classes"
	"git.golem15.com/golem15/sm-user-plugin/models"
	"git.golem15.com/golem15/summercms/modules/cabana"
	"git.golem15.com/golem15/summercms/modules/pact"
	"git.golem15.com/golem15/summercms/modules/phrasebook"
	"gorm.io/gorm"
)

var _ pact.HasAccountContributions = (*Plugin)(nil)

// backendLinkLang prefixes the phrase keys of the account link.
const backendLinkLang = "golem15.user::lang.backend_link."

// AccountContributions adds the "Frontend account" section to the admin's
// My account page (D-04): its status names the linked frontend account,
// "link" starts a link request and answers the site URL the administrator
// opens to sign in there as the frontend user and confirm (D-05; the link is
// written only by that confirmation), and "unlink" removes the link.
func (p *Plugin) AccountContributions() []pact.AccountContribution {
	return []pact.AccountContribution{{
		Name:        "frontend_account",
		Label:       backendLinkLang + "section",
		Description: backendLinkLang + "section_comment",
		Status:      p.frontendAccountStatus,
		Actions: []pact.AccountAction{
			{
				Name:  "link",
				Label: backendLinkLang + "link",
				Applies: func(ctx context.Context, adminID uint) (bool, error) {
					link, err := p.backendLinks().LinkFor(ctx, adminID)
					return link == nil, err
				},
				Run: p.startFrontendLink,
			},
			{
				Name:    "unlink",
				Label:   backendLinkLang + "unlink",
				Confirm: backendLinkLang + "unlink_confirm",
				Danger:  true,
				Applies: func(ctx context.Context, adminID uint) (bool, error) {
					link, err := p.backendLinks().LinkFor(ctx, adminID)
					return link != nil, err
				},
				Run: p.unlinkOwnFrontendAccount,
			},
		},
	}}
}

// backendLinks returns the published link service, or one over the app.
func (p *Plugin) backendLinks() *classes.BackendLinks {
	if p.app != nil {
		if links, ok := p.app.Lookup[*classes.BackendLinks](); ok && links != nil {
			return links
		}
	}
	return &classes.BackendLinks{App: p.app}
}

// frontendAccountStatus answers "Linked to <email>" or "Not linked" in the
// request locale for the signed-in administrator.
func (p *Plugin) frontendAccountStatus(ctx context.Context, adminID uint) (string, error) {
	link, err := p.backendLinks().LinkFor(ctx, adminID)
	if err != nil {
		return "", err
	}
	if link == nil {
		return backendLinkLang + "status_unlinked", nil
	}
	email, err := p.frontendEmail(ctx, link.UserID)
	if err != nil {
		return "", err
	}
	const key = backendLinkLang + "status_linked"
	if p.app != nil {
		if tr, ok := p.app.Lookup[*phrasebook.Translator](); ok && tr != nil {
			if text := tr.Get(ctx, key, map[string]string{"email": email}); text != "" && text != key {
				return text, nil
			}
		}
	}
	return "Linked to " + email, nil
}

// frontendEmail reads the email of a frontend user, deactivated or not.
func (p *Plugin) frontendEmail(ctx context.Context, userID uint) (string, error) {
	var db *gorm.DB
	if tx, ok := cabana.TxFromContext(ctx); ok {
		db = tx.Session(&gorm.Session{NewDB: true})
	} else if p.app != nil {
		db, _ = p.app.Lookup[*gorm.DB]()
	}
	if db == nil {
		return "", errors.New("golem15.user: gorm handle is missing")
	}
	var emails []string
	if err := db.WithContext(ctx).Unscoped().Model(&models.User{}).Where("id = ?", userID).Pluck("email", &emails).Error; err != nil {
		return "", err
	}
	if len(emails) == 0 {
		return "", nil
	}
	return emails[0], nil
}

// startFrontendLink creates a link request for the signed-in administrator
// and answers the site page that confirms it:
// golem15.user.frontend_url (else app.url) + /link-admin?code=<code>.
func (p *Plugin) startFrontendLink(ctx context.Context, in pact.AccountActionInput) (pact.AccountActionResult, error) {
	plain, _, err := p.backendLinks().CreateLinkRequest(ctx, in.AdminID)
	if err != nil {
		return pact.AccountActionResult{}, err
	}
	return pact.AccountActionResult{
		Message: backendLinkLang + "link_started",
		URL:     classes.FrontendURL(p.app) + "/link-admin?code=" + plain,
	}, nil
}

// unlinkOwnFrontendAccount removes the signed-in administrator's link in
// the action's transaction.
func (p *Plugin) unlinkOwnFrontendAccount(ctx context.Context, in pact.AccountActionInput) (pact.AccountActionResult, error) {
	tx, ok := cabana.TxFromContext(ctx)
	if !ok {
		return pact.AccountActionResult{}, errors.New("golem15.user: unlinking needs the action's transaction")
	}
	links := p.backendLinks()
	link, err := links.LinkFor(ctx, in.AdminID)
	if err != nil {
		return pact.AccountActionResult{}, err
	}
	if err := links.RemoveLink(ctx, tx, link); err != nil {
		return pact.AccountActionResult{}, err
	}
	return pact.AccountActionResult{Message: backendLinkLang + "unlinked"}, nil
}