package handlers

import (
	"net/http"
	"strconv"
	"strings"

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

// parseRetentionDays interprets a retention_days form value. It
// returns the number of days, or, for a value it refuses, the message
// the create and edit forms show; the message is empty when the value
// is accepted.
//
// An empty value yields fallback, which lets the create path apply the
// default and the edit path leave the stored value unchanged. A value
// of 0 is returned as 0 and is rewritten to the retain-forever
// sentinel by database.Webhook's BeforeSave hook. Anything unparseable
// or negative is refused rather than silently given a default.
//
// The upper bound is not cosmetic. The reaper computes its cutoff as a
// time.Duration, an int64 nanosecond count, so a day count above
// database.MaxFiniteRetentionDays overflows, puts the cutoff in the
// future, and deletes every event the webhook has. A finite value
// above that ceiling is therefore refused, and the message names the
// ceiling rather than implying the input was not a number.
//
// A value at or above the retain-forever sentinel is not out of range:
// it is what the edit form pre-fills for a retain-forever webhook, so
// submitting the form back unchanged has to keep meaning "forever"
// rather than being rejected.
func parseRetentionDays(raw string, fallback int) (int, string) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return fallback, ""
	}

	v, err := strconv.Atoi(raw)
	if err != nil || v < 0 {
		return 0, "Retention must be a whole number of days, or 0 to " +
			"retain events forever."
	}

	if v >= database.RetentionForeverDays {
		return database.RetentionForeverDays, ""
	}

	if v > database.MaxFiniteRetentionDays {
		return 0, "Retention must be at most " +
			strconv.Itoa(database.MaxFiniteRetentionDays) +
			" days, or 0 to retain events forever."
	}

	return v, ""
}

// ownedWebhook resolves the request's sourceID parameter to a
// webhook the session's user owns.
//
// Ownership and existence are decided by one query, so a
// webhook belonging to another user is indistinguishable from
// one that does not exist: both are a 404, and neither confirms
// the id. Callers that reach further into a webhook's data —
// the event log page and the event body download — share this
// one check rather than restating it, so the download cannot
// come to authorize differently from the page that links to it.
//
// It reports false once it has written the response, which is a
// redirect to the login page for an unauthenticated request and
// a 404 otherwise. The caller returns without writing more.
func (h *Handlers) ownedWebhook(
	w http.ResponseWriter,
	r *http.Request,
) (database.Webhook, bool) {
	var webhook database.Webhook

	userID, ok := h.getUserID(r)
	if !ok {
		http.Redirect(
			w, r, "/pages/login", http.StatusSeeOther,
		)

		return database.Webhook{}, false
	}

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

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

		return database.Webhook{}, false
	}

	return webhook, true
}

// deleteChildResource returns a handler that deletes a child
// resource (entrypoint or target) belonging to a webhook. The
// optional afterDelete hook runs with the child's id once the
// delete has removed it, before the redirect, which carries done as
// its notice.
func (h *Handlers) deleteChildResource(
	idParam string,
	model any,
	errMsg string,
	afterDelete func(childID string),
	done noticeCode,
) 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")
		childID := chi.URLParam(r, idParam)

		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
		}

		result := h.db.DB().Where(
			"id = ? AND webhook_id = ?",
			childID, webhook.ID,
		).Delete(model)
		if result.Error != nil {
			h.serverError(w, r, errMsg, result.Error)

			return
		}

		// Only for a row this webhook really had: the id came from
		// the URL and may name another webhook's child.
		if afterDelete != nil && result.RowsAffected > 0 {
			afterDelete(childID)
		}

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

// toggleChildResource returns a handler that toggles the active
// state of a child resource belonging to a webhook. toggleFn returns
// the new state, and the redirect carries activated or deactivated as
// its notice to match.
func (h *Handlers) toggleChildResource(
	idParam string,
	toggleFn func(webhookID, childID string) (bool, error),
	errMsg string,
	activated, deactivated noticeCode,
) 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")
		childID := chi.URLParam(r, idParam)

		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
		}

		active, err := toggleFn(webhook.ID, childID)
		if err != nil {
			h.serverError(w, r, errMsg, err)

			return
		}

		done := deactivated
		if active {
			done = activated
		}

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

// getUserID extracts the user ID from the session.
func (h *Handlers) getUserID(
	r *http.Request,
) (string, bool) {
	sess, err := h.session.Get(r)
	if err != nil {
		return "", false
	}

	if !h.session.IsAuthenticated(sess) {
		return "", false
	}

	return h.session.GetUserID(sess)
}