package handlers

import (
	"errors"
	"net/http"
	"strconv"

	"github.com/go-chi/chi"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/delivery"
)

// HandleSourceEdit shows the form to edit a webhook.
func (h *Handlers) HandleSourceEdit() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		userID, ok := h.getUserID(r)
		if !ok {
			http.Redirect(
				w, r, "/pages/login", http.StatusSeeOther,
			)

			return
		}

		sourceID := chi.URLParam(r, "sourceID")

		var webhook database.Webhook

		err := h.db.DB().Where(
			"id = ? AND user_id = ?", sourceID, userID,
		).First(&webhook).Error
		if err != nil {
			h.renderError(w, r, http.StatusNotFound)

			return
		}

		h.renderWebhookEdit(
			w, r, &webhook,
			webhook.Name, webhook.Description,
			strconv.Itoa(webhook.RetentionDays),
			"", http.StatusOK,
		)
	}
}

// HandleSourceEditSubmit handles the webhook edit form
// submission.
func (h *Handlers) HandleSourceEditSubmit() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		userID, ok := h.getUserID(r)
		if !ok {
			http.Redirect(
				w, r, "/pages/login", http.StatusSeeOther,
			)

			return
		}

		sourceID := chi.URLParam(r, "sourceID")

		h.renameMu.Lock()
		defer h.renameMu.Unlock()

		var webhook database.Webhook

		err := h.db.DB().Where(
			"id = ? AND user_id = ?", sourceID, userID,
		).First(&webhook).Error
		if err != nil {
			h.renderError(w, r, http.StatusNotFound)

			return
		}

		// The body size cap is enforced by the MaxBodySize
		// middleware, which runs before CSRF parses the form.
		err = r.ParseForm()
		if err != nil {
			h.renderError(w, r, http.StatusBadRequest)

			return
		}

		h.applyWebhookEdit(w, r, &webhook)
	}
}

// applyWebhookEdit validates and saves webhook edits. A refused save
// shows the edit form again with the values submitted and the reason.
func (h *Handlers) applyWebhookEdit(
	w http.ResponseWriter,
	r *http.Request,
	webhook *database.Webhook,
) {
	// The body size cap is enforced by the MaxBodySize middleware,
	// which runs before CSRF parses the form.
	name := r.PostFormValue("name")
	description := r.PostFormValue("description")
	retention := r.PostFormValue("retention_days")

	if name == "" {
		h.renderWebhookEdit(
			w, r, webhook, name, description, retention,
			"Name is required", http.StatusBadRequest,
		)

		return
	}

	// An empty field falls back to the stored value, so submitting the
	// form without touching retention leaves the policy alone.
	retentionDays, errMsg := parseRetentionDays(
		retention, webhook.RetentionDays,
	)
	if errMsg != "" {
		h.renderWebhookEdit(
			w, r, webhook, name, description, retention,
			errMsg, http.StatusBadRequest,
		)

		return
	}

	// edited is the webhook as the submission leaves it; webhook stays
	// as stored, for the page shown again when the save is refused.
	edited := *webhook
	edited.Name = name
	edited.Description = description
	edited.RetentionDays = retentionDays

	// A new name renames the archive files before it is saved (see
	// delivery.Engine.Rename). If either step fails, the same targets'
	// archives go back to the name that is still stored, without
	// reading the main database again.
	targets, err := h.renameWebhookArchives(
		webhook.ID, webhook.Name, edited.Name,
	)
	if err == nil {
		err = h.db.DB().Save(&edited).Error
	}

	if err != nil {
		restoreErr := h.renameArchives(targets, webhook.Name)
		if restoreErr != nil {
			h.log.Error(
				"failed to rename archives back",
				"webhook_id", webhook.ID,
				"error", restoreErr,
			)
		}

		if errors.Is(err, delivery.ErrArchiveNameTaken) {
			h.renderWebhookEdit(
				w, r, webhook, name, description, retention,
				"Not saved: "+err.Error()+
					". Move that archive out of the data directory, "+
					"its .db together with any -wal and -shm beside "+
					"it, then save again.",
				http.StatusConflict,
			)

			return
		}

		h.serverError(w, r, "failed to update webhook", err)

		return
	}

	http.Redirect(
		w, r, withNotice("/hook/"+webhook.ID, webhookSaved),
		http.StatusSeeOther,
	)
}

// renderWebhookEdit renders the webhook edit page for the webhook as
// stored, its form showing name, description and retentionDays, with
// an optional error message above it.
func (h *Handlers) renderWebhookEdit(
	w http.ResponseWriter,
	r *http.Request,
	webhook *database.Webhook,
	name, description, retentionDays, errMsg string,
	status int,
) {
	data := map[string]any{
		tmplKeyWebhook:  webhook,
		tmplKeyError:    errMsg,
		"Name":          name,
		"Description":   description,
		"RetentionDays": retentionDays,
	}

	h.renderTemplateStatus(w, r, "source_edit.html", data, status)
}

// renameWebhookArchives renames the archive file of every database
// target of a webhook from the webhook name oldName to newName,
// keeping each target's own name. It does nothing when the name is
// unchanged. It returns the targets it read, so that a failed edit can
// move those same archives back with renameArchives.
func (h *Handlers) renameWebhookArchives(
	webhookID, oldName, newName string,
) ([]database.Target, error) {
	if h.archives == nil || oldName == newName {
		return nil, nil
	}

	var targets []database.Target

	err := h.db.DB().
		Where(
			"webhook_id = ? AND type = ?",
			webhookID, database.TargetTypeDatabase,
		).
		Find(&targets).Error
	if err != nil {
		return nil, err
	}

	return targets, h.renameArchives(targets, newName)
}

// renameArchives renames the archive file of each of the given
// database targets to the webhook name webhookName, keeping each
// target's own name. It tries every target even after one fails, so
// that moving the archives back after a failed edit leaves none under
// the new name, and returns every failure joined.
func (h *Handlers) renameArchives(
	targets []database.Target, webhookName string,
) error {
	var errs []error

	for i := range targets {
		err := h.archives.Rename(
			targets[i].ID, webhookName, targets[i].Name,
		)
		if err != nil {
			errs = append(errs, err)
		}
	}

	return errors.Join(errs...)
}