// Copyright (C) 2026 Dcntrlized
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package actions

import (
	"errors"
	"net/http"
	"strings"
	"time"

	"git.dcntrlized.org/Dcntrlized/Alarm/db"
	"git.dcntrlized.org/Dcntrlized/Alarm/internal/alertstate"
	"git.dcntrlized.org/Dcntrlized/Alarm/internal/deviceid"
	"git.dcntrlized.org/Dcntrlized/Alarm/realtime"
)

// actionResponse is the trigger/disarm result.
type actionResponse struct {
	EventID    string `json:"eventId"`
	Action     string `json:"action"`
	ServerTime string `json:"serverTime"`
	Delivered  int    `json:"delivered"`
}

type triggerRequest struct {
	AlertID    string  `json:"alertId"`
	AdminToken string  `json:"adminToken"`
	Message    *string `json:"message"`
}

// TriggerAlert implements POST /action/triggerAlert.
//
// The state transition and the event row are written in one transaction, and
// the schema's NOTIFY trigger publishes the event on commit, so every service
// instance fans it out. This instance additionally broadcasts in-process for
// the fast path; the hub de-duplicates the two by event id.
func TriggerAlert(w http.ResponseWriter, r *http.Request, payload any) {
	const action = "triggerAlert"
	alert, p, ok := requireAdminToken(w, r, action, payload)
	if !ok {
		return
	}

	var req triggerRequest
	_ = decodePayload(payload, &req)
	message := alert.Message
	if req.Message != nil {
		m, err := validateMessage(*req.Message)
		if err != nil {
			validationError(w, "%v", err)
			return
		}
		if strings.TrimSpace(m) != "" {
			message = &m
		}
	}

	updated, event, err := db.TriggerAlert(r.Context(), alert.ID, p.ID, message)
	if err != nil {
		dbError(w, action, err)
		return
	}

	delivered := 0
	if hub := realtime.Current(); hub != nil {
		delivered = hub.Broadcast(updated.ID, realtime.AlarmFrame{
			Type:       "alarm",
			AlertID:    updated.ID.String(),
			EventID:    event.ID.String(),
			Action:     alertstate.KindTrigger,
			Message:    deref(event.Message),
			ServerTime: rfc3339(event.CreatedAt),
		})
	}

	Debug(action, "POST", "alert=%s event=%s delivered=%d", updated.ID, event.ID, delivered)
	writeJSON(w, http.StatusOK, actionResponse{
		EventID:    event.ID.String(),
		Action:     alertstate.KindTrigger,
		ServerTime: rfc3339(event.CreatedAt),
		Delivered:  delivered,
	})
}

// DisarmAlert implements POST /action/disarmAlert.
func DisarmAlert(w http.ResponseWriter, r *http.Request, payload any) {
	const action = "disarmAlert"
	alert, p, ok := requireAdminToken(w, r, action, payload)
	if !ok {
		return
	}

	updated, event, err := db.DisarmAlert(r.Context(), alert.ID, p.ID, nil)
	if err != nil {
		dbError(w, action, err)
		return
	}

	delivered := 0
	if hub := realtime.Current(); hub != nil {
		delivered = hub.Broadcast(updated.ID, realtime.AlarmFrame{
			Type:       "alarm",
			AlertID:    updated.ID.String(),
			EventID:    event.ID.String(),
			Action:     alertstate.KindDisarm,
			Message:    deref(event.Message),
			ServerTime: rfc3339(event.CreatedAt),
		})
	}

	Debug(action, "POST", "alert=%s event=%s delivered=%d", updated.ID, event.ID, delivered)
	writeJSON(w, http.StatusOK, actionResponse{
		EventID:    event.ID.String(),
		Action:     alertstate.KindDisarm,
		ServerTime: rfc3339(event.CreatedAt),
		Delivered:  delivered,
	})
}

// offlineAlarmResponse is the 409 check-in body: the standard error envelope plus
// the alarm frame the device missed while offline. 409 is a status, not a
// failure: it means "an alarm is pending and must ring now".
type offlineAlarmResponse struct {
	Error struct {
		Code    string `json:"code"`
		Message string `json:"message"`
	} `json:"error"`
	Alarm realtime.AlarmFrame `json:"alarm"`
}

// writeOfflineAlarm answers alarmStatus with 409 ERR_ALARM_TRIGGERED_OFFLINE and
// the missed trigger frame. The frame is the same shape the socket would have
// delivered (same eventId, same serverTime), so the client renders an offline
// alarm with the code path it already has for a live one.
func writeOfflineAlarm(w http.ResponseWriter, alert *db.Alert, pending *db.PendingDelivery) {
	message := ""
	switch {
	case pending.Message != nil:
		message = *pending.Message
	case alert.Message != nil:
		message = *alert.Message
	}

	var body offlineAlarmResponse
	body.Error.Code = CodeAlarmTriggeredOffline
	body.Error.Message = "an alarm was triggered while this device was offline; ring now"
	body.Alarm = realtime.AlarmFrame{
		Type:       "alarm",
		AlertID:    alert.ID.String(),
		EventID:    pending.EventID.String(),
		Action:     alertstate.KindTrigger,
		Message:    message,
		ServerTime: rfc3339(pending.ServerTime),
	}
	writeJSON(w, http.StatusConflict, body)
}

// statusView is the alarmStatus polling fallback payload (frozen field set).
type statusView struct {
	Active     bool   `json:"active"`
	EventID    string `json:"eventId"`
	Action     string `json:"action"`
	Message    string `json:"message"`
	ServerTime string `json:"serverTime"`
}

// AlarmStatus implements GET/POST /action/alarmStatus: the cheap, indexed
// fallback a client polls when its socket is down or it was killed mid-alarm. It
// also serves as the offline check-in (409 ERR_ALARM_TRIGGERED_OFFLINE) and is
// where a missed alarm's ledger row is retired.
//
// `active` is derived from the commanded status, never stored and never
// clock-based: an alert is active from trigger until the owner disarms it, so no
// background job is needed to expire anything.
func AlarmStatus(w http.ResponseWriter, r *http.Request, payload any) {
	const action = "alarmStatus"
	c, ok := callerFor(w, r, action)
	if !ok {
		return
	}
	alertID, err := alertIDFrom(r, payload)
	if err != nil {
		validationError(w, "%v", err)
		return
	}

	res, err := db.GetAlertWithLatestEvent(r.Context(), alertID)
	if err != nil {
		dbError(w, action, err)
		return
	}
	if c.IsDevice {
		if !c.subscribedTo(alertID) {
			writeError(w, http.StatusNotFound, CodeAlertNotSubscribed, "not subscribed to this alert")
			return
		}
	} else {
		allowed, err := isAdminOrSubscriber(r, res.Alert, c.UserID)
		if err != nil {
			dbError(w, action, err)
			return
		}
		if !allowed {
			writeError(w, http.StatusNotFound, CodeAlertNotSubscribed, "not subscribed to this alert")
			return
		}
	}

	// Offline check-in, READ-ONLY. If this device still owes an alarm, answer
	// with the frame it missed instead of a quiet 200 — and clear NOTHING. The
	// debt is settled only by an explicit ack (ackAlarm or the WS ack), because a
	// 409 lost in transit must not forfeit the alarm: the next check-in has to
	// find the same row. A trigger that has since been disarmed is not news, so
	// that case falls through to the normal body (active:false).
	deviceHash := ""
	if !c.IsDevice {
		if raw := strings.TrimSpace(r.URL.Query().Get("deviceId")); raw != "" {
			deviceHash = deviceid.Hash(raw)
		}
	}
	var pending *db.PendingDelivery
	if c.IsDevice {
		// The device token already identifies the subscription, so its whole
		// pending set is the debt to report.
		rows, err := db.PendingReplay(r.Context(), alertID, c.Sub.ID)
		if err != nil && !errors.Is(err, db.ErrNotFound) {
			dbError(w, action, err)
			return
		}
		if len(rows) > 0 {
			pending = &rows[0]
		}
	} else {
		var err error
		pending, err = db.PendingTrigger(r.Context(), alertID, c.UserID, deviceHash)
		if err != nil && !errors.Is(err, db.ErrNotFound) {
			dbError(w, action, err)
			return
		}
	}
	if pending != nil && res.Event != nil && res.Event.Kind == alertstate.KindTrigger {
		writeOfflineAlarm(w, res.Alert, pending)
		return
	}

	now := time.Now().UTC()
	active := alertstate.IsActive(res.Alert.Status)
	if res.Event == nil || res.Event.Kind != alertstate.KindTrigger {
		// A never-triggered alert, or one whose newest event is a disarm, is
		// not live even if the stored status says "triggered".
		active = false
	}
	// "Active" is a statement about THIS caller, not about the alert's commanded
	// status. The alert stays triggered until the owner disarms it or every
	// subscriber acknowledges, so answering a device that already dismissed the
	// alarm with active:true makes a correct client re-raise the takeover on
	// every poll — the alarm that will not stay dismissed. A subscriber is
	// active only while it still owes the newest trigger; the owner (who has no
	// delivery row) keeps seeing their own alert as live.
	callerIsOwner := !c.IsDevice && res.Alert.AdminUserID == c.UserID
	if active && !callerIsOwner {
		var owed bool
		if c.IsDevice {
			owed, err = db.HasPendingDelivery(r.Context(), alertID, c.Sub.ID)
		} else {
			owed, err = db.HasPendingDeliveryForUser(r.Context(), alertID, c.UserID, deviceHash)
		}
		if err != nil {
			dbError(w, action, err)
			return
		}
		active = owed
	}

	view := statusView{
		Active:     active,
		ServerTime: rfc3339(now),
	}
	if res.Event != nil {
		view.EventID = res.Event.ID.String()
		view.Action = res.Event.Kind
		view.Message = deref(res.Event.Message)
		view.ServerTime = rfc3339(res.Event.CreatedAt)
	}
	writeJSON(w, http.StatusOK, view)
}