// The Hub contract surface (AGENTS.md §4 FR-11, §8, §10 rule 5, §11 Phase 8).
//
// The project side of central_ai_llm_master/docs/ask-contract.md:
//
//	GET  /capabilities  -> the topics this service answers (Hub routing)
//	POST /ask           -> one short, read-only answer about school work
//	POST /notify        -> accept the contract's notification and deliver it
//
// All three require the shared Hub bearer token (SCHOOL_HUB_TOKEN). A
// service-to-service call must never be trusted unsigned. /ask and
// /capabilities are read-only: they call only store read methods. /notify is
// the one write on this surface, and it only records and delivers a message;
// it never changes school data and never touches the school (AGENTS.md §10
// rule 1).
package web

import (
	"context"
	"crypto/subtle"
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"

	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/apprise"
	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/config"
	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/hub"
	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/store"
)

// hubMaxBody bounds a Hub request body. Questions and notifications are small.
const hubMaxBody = 64 << 10 // 64 KiB

// notifyResponse is this service's own reply to POST /notify. The contract does
// not freeze a response shape for the receiver, so this is kept minimal and
// matches the sibling project.
type notifyResponse struct {
	OK    bool   `json:"ok"`
	Error string `json:"error,omitempty"`
}

// hubAuthOK enforces the shared bearer token on the Hub endpoints. It writes
// the refusal and returns false when the request may not be served. askShape
// selects the contract-shaped body for /ask; the other endpoints get the
// minimal error body.
func (s *Server) hubAuthOK(w http.ResponseWriter, r *http.Request, askShape bool) bool {
	refuse := func(code int, reason string) {
		if askShape {
			s.writeJSON(w, code, hub.AskResponse{Answer: nil, Reason: reason})
			return
		}
		s.writeJSON(w, code, notifyResponse{Error: reason})
	}
	if !s.cfg.HubConfigured() {
		s.log.Warn("hub api disabled: SCHOOL_HUB_TOKEN is not set", "path", r.URL.Path)
		refuse(http.StatusServiceUnavailable, "the Hub API is not configured")
		return false
	}
	provided := bearerTokenOf(r)
	if subtle.ConstantTimeCompare([]byte(provided), []byte(strings.TrimSpace(s.cfg.HubToken))) != 1 {
		s.log.Warn("hub api rejected", "path", r.URL.Path, "remote", r.RemoteAddr)
		w.Header().Set("WWW-Authenticate", `Bearer realm="compass-nhs"`)
		refuse(http.StatusUnauthorized, "unauthorized")
		return false
	}
	return true
}

// handleCapabilities returns the routing topics for the Hub. It holds no
// private data.
func (s *Server) handleCapabilities(w http.ResponseWriter, r *http.Request) {
	if !s.hubAuthOK(w, r, false) {
		return
	}
	s.writeJSON(w, http.StatusOK, hub.DefaultCapabilities())
}

// handleAsk answers one question from this project's read-only data. The reply
// is always HTTP 200 with either an answer or a reason, so the Hub can relay a
// "cannot answer" without treating the project as down.
func (s *Server) handleAsk(w http.ResponseWriter, r *http.Request) {
	if !s.hubAuthOK(w, r, true) {
		return
	}
	// The contract caps the answer at 3 seconds; the timeout leaves room for the
	// write rather than cutting off mid-reply.
	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
	defer cancel()

	var req hub.AskRequest
	dec := json.NewDecoder(http.MaxBytesReader(w, r.Body, hubMaxBody))
	if err := dec.Decode(&req); err != nil {
		s.writeJSON(w, http.StatusOK, hub.AskResponse{
			Answer: nil,
			Reason: "the request body is not valid JSON",
		})
		return
	}

	started := time.Now()
	resp := s.answerer.Answer(ctx, req)
	s.log.Info("hub ask",
		"asker", req.Asker,
		"person", req.Person,
		"source", req.Source,
		"question", req.Question,
		"answered", resp.Answer != nil,
		"reason", resp.Reason,
		"duration_ms", time.Since(started).Milliseconds(),
	)
	s.writeJSON(w, http.StatusOK, resp)
}

// handleNotify accepts a notification in the frozen contract's shape and
// delivers it to the named person through Apprise. The message is recorded
// before delivery, so a delivery failure is visible on the dashboard and in
// `notifications` (FR-12).
func (s *Server) handleNotify(w http.ResponseWriter, r *http.Request) {
	if !s.hubAuthOK(w, r, false) {
		return
	}
	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()

	var req hub.NotifyRequest
	dec := json.NewDecoder(http.MaxBytesReader(w, r.Body, hubMaxBody))
	if err := dec.Decode(&req); err != nil {
		s.writeJSON(w, http.StatusBadRequest, notifyResponse{Error: "invalid JSON body"})
		return
	}

	from := strings.TrimSpace(req.From)
	if from == "" {
		from = hub.ProjectName
	}
	level := strings.ToLower(strings.TrimSpace(req.Level))
	switch level {
	case "":
		level = "info"
	case "info", "important", "urgent":
	default:
		s.writeJSON(w, http.StatusBadRequest, notifyResponse{Error: "level must be info, important or urgent"})
		return
	}
	message := strings.TrimSpace(req.Message)
	if message == "" {
		s.writeJSON(w, http.StatusBadRequest, notifyResponse{Error: "message is required"})
		return
	}
	if len(message) > 500 {
		message = message[:500]
	}

	recipient, err := s.notifyRecipient(req.Person)
	if err != nil {
		s.writeJSON(w, http.StatusBadRequest, notifyResponse{Error: err.Error()})
		return
	}
	if !s.cfg.Apprise.Enabled() {
		s.writeJSON(w, http.StatusServiceUnavailable, notifyResponse{
			Error: "apprise is not configured: set " + strings.Join(s.cfg.Apprise.Missing(), ", "),
		})
		return
	}
	if s.apprise == nil || !s.apprise.Configured() {
		s.writeJSON(w, http.StatusServiceUnavailable, notifyResponse{Error: "apprise is not configured"})
		return
	}

	title := "Compass / NHS — " + from
	channels := s.cfg.Apprise.Channels
	if len(channels) == 0 {
		channels = []string{config.ChannelEmail}
	}

	now := time.Now()
	failed := 0
	for _, ch := range channels {
		tag := s.cfg.Apprise.ChannelTag(recipient, ch)
		res, sendErr := s.apprise.SendTags(ctx, []string{tag}, title, message, notifyType(level))
		n := store.Notification{
			Scope:     "hub",
			Recipient: recipient.Name,
			Channel:   ch,
			Tag:       tag,
			Text:      message,
			OK:        sendErr == nil,
		}
		if sendErr != nil {
			n.Error = apprise.Truncate(sendErr.Error(), 300)
			failed++
		} else {
			sent := now
			n.SentAt = &sent
		}
		if _, recErr := s.store.RecordNotification(ctx, n); recErr != nil {
			s.log.Error("hub notify record", "recipient", recipient.Name, "err", recErr)
		}
		if sendErr != nil {
			s.log.Error("hub notify NOT delivered", "recipient", recipient.Name, "channel", ch, "tag", tag,
				"status", res.Status, "err", n.Error)
		} else {
			s.log.Info("hub notify delivered", "from", from, "level", level, "recipient", recipient.Name,
				"channel", ch, "tag", tag, "status", res.Status)
		}
	}

	if failed > 0 {
		s.writeJSON(w, http.StatusBadGateway, notifyResponse{Error: fmt.Sprintf("delivery failed on %d channel(s)", failed)})
		return
	}
	s.writeJSON(w, http.StatusOK, notifyResponse{OK: true})
}

// notifyRecipient resolves the contract's `person` to a configured Apprise
// recipient. An empty person defaults to Sam, the service's owner; an unknown
// person is refused rather than delivered to the wrong inbox.
func (s *Server) notifyRecipient(person string) (config.Recipient, error) {
	person = strings.TrimSpace(person)
	if person == "" {
		if r, ok := s.cfg.Apprise.RecipientByName("Sam"); ok {
			return r, nil
		}
		if parents := s.cfg.Apprise.ParentRecipients(); len(parents) > 0 {
			return parents[0], nil
		}
		return config.Recipient{}, fmt.Errorf("no recipient is configured")
	}
	r, ok := s.cfg.Apprise.RecipientByName(person)
	if !ok {
		return config.Recipient{}, fmt.Errorf("unknown person %q", person)
	}
	return r, nil
}

// notifyType maps the contract's level to an Apprise notification class.
func notifyType(level string) string {
	switch level {
	case "important":
		return apprise.TypeWarning
	case "urgent":
		return apprise.TypeFailure
	default:
		return apprise.TypeInfo
	}
}

// bearerTokenOf reads the bearer token from the Authorization header,
// case-insensitively.
func bearerTokenOf(r *http.Request) string {
	h := strings.TrimSpace(r.Header.Get("Authorization"))
	if len(h) < 7 || !strings.EqualFold(h[:7], "bearer ") {
		return ""
	}
	return strings.TrimSpace(h[7:])
}