package handlers

import (
	"encoding/json"
	"errors"
	"net/http"
	"strconv"
	"time"

	"github.com/go-chi/chi/v5"

	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/auth"
	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/models"
	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/store"
)

type TopicsHandler struct {
	store *store.TopicStore
}

func NewTopicsHandler(s *store.TopicStore) *TopicsHandler { return &TopicsHandler{store: s} }

// GET /api/topics?status=...&visibility=...&limit=...&offset=...
//
// Visibility filter is enforced at the auth layer: anonymous callers
// only see visibility=public; authenticated users (CallerUser) see all
// they're entitled to (Phase 2 v1: all; Phase 4 may add per-user ACLs).
// Agent callers (CallerAgent) see all — they're acting as system on
// behalf of the platform.
func (h *TopicsHandler) List(w http.ResponseWriter, r *http.Request) {
	caller := auth.FromContext(r.Context())
	f := store.ListFilter{
		Status:     r.URL.Query().Get("status"),
		Visibility: r.URL.Query().Get("visibility"),
	}
	if v, _ := strconv.Atoi(r.URL.Query().Get("limit")); v > 0 {
		f.Limit = v
	}
	if v, _ := strconv.Atoi(r.URL.Query().Get("offset")); v > 0 {
		f.Offset = v
	}

	// Anonymous: force visibility=public.
	if caller.Kind == "" {
		f.Visibility = string(models.VisibilityPublic)
	}

	rows, err := h.store.List(r.Context(), f)
	if err != nil {
		http.Error(w, "list failed: "+err.Error(), http.StatusInternalServerError)
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"topics": rows, "count": len(rows)})
}

// GET /api/topics/{id}
func (h *TopicsHandler) Get(w http.ResponseWriter, r *http.Request) {
	id := chi.URLParam(r, "id")
	if id == "" {
		http.Error(w, "missing id", http.StatusBadRequest)
		return
	}
	t, err := h.store.GetByID(r.Context(), id)
	if errors.Is(err, store.ErrNotFound) {
		http.Error(w, "topic not found", http.StatusNotFound)
		return
	}
	if err != nil {
		http.Error(w, "get failed: "+err.Error(), http.StatusInternalServerError)
		return
	}
	// Visibility gate: anonymous can only see public; authenticated see all.
	caller := auth.FromContext(r.Context())
	if caller.Kind == "" && t.Visibility != models.VisibilityPublic {
		http.Error(w, "not found", http.StatusNotFound) // 404 not 403 — hide existence
		return
	}
	writeJSON(w, http.StatusOK, t)
}

type createTopicBody struct {
	Title           string `json:"title"`
	Summary         string `json:"summary"`
	Visibility      string `json:"visibility"`        // default "private"
	VerdictSchemaID string `json:"verdict_schema_id"` // default "free-form"
	SignupOpenAt    string `json:"signup_open_at"`    // RFC3339
	SignupCloseAt   string `json:"signup_close_at"`
	DebateStartAt   string `json:"debate_start_at"`
	DebateEndAt     string `json:"debate_end_at"`
}

// POST /api/topics
//
// Allowed callers: agent or authenticated user. Anonymous rejected
// (the route wires the auth-required middleware).
func (h *TopicsHandler) Create(w http.ResponseWriter, r *http.Request) {
	caller := auth.FromContext(r.Context())
	if caller.Kind == "" {
		http.Error(w, "auth required", http.StatusUnauthorized)
		return
	}
	var body createTopicBody
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		http.Error(w, "bad body: "+err.Error(), http.StatusBadRequest)
		return
	}
	if body.Title == "" || body.Summary == "" {
		http.Error(w, "title and summary required", http.StatusBadRequest)
		return
	}
	if body.Visibility == "" {
		body.Visibility = string(models.VisibilityPrivate)
	}
	if body.VerdictSchemaID == "" {
		body.VerdictSchemaID = "free-form"
	}
	if err := validateLifecycleTimes(body); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	created, err := h.store.Create(r.Context(), store.CreateTopicInput{
		Title:           body.Title,
		Summary:         body.Summary,
		Visibility:      models.Visibility(body.Visibility),
		VerdictSchemaID: body.VerdictSchemaID,
		SignupOpenAt:    body.SignupOpenAt,
		SignupCloseAt:   body.SignupCloseAt,
		DebateStartAt:   body.DebateStartAt,
		DebateEndAt:     body.DebateEndAt,
		CreatorUserID:   caller.ID,
	})
	if err != nil {
		http.Error(w, "create failed: "+err.Error(), http.StatusInternalServerError)
		return
	}
	writeJSON(w, http.StatusCreated, created)
}

// validateLifecycleTimes enforces:
//
//	signup_open < signup_close <= debate_start < debate_end
//
// All four timestamps must be parsable as RFC3339; failure → 400.
func validateLifecycleTimes(b createTopicBody) error {
	type p struct {
		name string
		raw  string
	}
	parts := []p{
		{"signup_open_at", b.SignupOpenAt},
		{"signup_close_at", b.SignupCloseAt},
		{"debate_start_at", b.DebateStartAt},
		{"debate_end_at", b.DebateEndAt},
	}
	parsed := make([]time.Time, 4)
	for i, x := range parts {
		t, err := time.Parse(time.RFC3339, x.raw)
		if err != nil {
			return errors.New(x.name + ": must be RFC3339")
		}
		parsed[i] = t
	}
	if !parsed[0].Before(parsed[1]) {
		return errors.New("signup_open_at must be before signup_close_at")
	}
	if parsed[1].After(parsed[2]) {
		return errors.New("signup_close_at must be <= debate_start_at")
	}
	if !parsed[2].Before(parsed[3]) {
		return errors.New("debate_start_at must be before debate_end_at")
	}
	return nil
}

// PUT /api/topics/{id}/visibility — admin-only flip (Phase 2 stub: any
// authenticated user; Phase 4 will check the dialectic-admin role from JWT).
func (h *TopicsHandler) SetVisibility(w http.ResponseWriter, r *http.Request) {
	caller := auth.FromContext(r.Context())
	if caller.Kind == "" {
		http.Error(w, "auth required", http.StatusUnauthorized)
		return
	}
	if caller.Kind == auth.CallerUser && !hasRole(caller, "dialectic-admin") {
		http.Error(w, "dialectic-admin role required", http.StatusForbidden)
		return
	}
	id := chi.URLParam(r, "id")
	var body struct {
		Visibility string `json:"visibility"`
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		http.Error(w, "bad body", http.StatusBadRequest)
		return
	}
	v := models.Visibility(body.Visibility)
	if v != models.VisibilityPublic && v != models.VisibilityPrivate {
		http.Error(w, "visibility must be public|private", http.StatusBadRequest)
		return
	}
	t, err := h.store.SetVisibility(r.Context(), id, v, caller.ID)
	if err != nil {
		http.Error(w, "update failed: "+err.Error(), http.StatusInternalServerError)
		return
	}
	writeJSON(w, http.StatusOK, t)
}

func hasRole(c auth.Caller, role string) bool {
	for _, r := range c.Roles {
		if r == role {
			return true
		}
	}
	return false
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("content-type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}