package handlers

import (
	"encoding/json"
	"errors"
	"net/http"
	"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 SignupsHandler struct {
	topics  *store.TopicStore
	signups *store.SignupStore
}

func NewSignupsHandler(t *store.TopicStore, s *store.SignupStore) *SignupsHandler {
	return &SignupsHandler{topics: t, signups: s}
}

type signupBody struct {
	WillingCamps []models.Camp `json:"willing_camps"`
	PreValidated bool          `json:"pre_validated"`
}

// POST /api/topics/{id}/signups
//
// Agent self-enrollment. Only CallerAgent is allowed — browsers can't
// sign up on behalf of an agent (would defeat the on_call pre-check
// that the plugin does before calling this endpoint).
//
// Body: { willing_camps: [pro|con|judge ...], pre_validated: bool }
//
// pre_validated is the agent's plugin's claim that it verified the
// agent has an on_call HF slot covering [debate_start_at, debate_end_at].
// Backend trusts but logs — Phase N may add server-side verification.
//
// Topic must be in status `signup_open`. Outside that window → 409.
func (h *SignupsHandler) Create(w http.ResponseWriter, r *http.Request) {
	caller := auth.FromContext(r.Context())
	if caller.Kind != auth.CallerAgent {
		http.Error(w, "signup is agent-only", http.StatusForbidden)
		return
	}
	topicID := chi.URLParam(r, "id")
	t, err := h.topics.GetByID(r.Context(), topicID)
	if errors.Is(err, store.ErrNotFound) {
		http.Error(w, "topic not found", http.StatusNotFound)
		return
	}
	if err != nil {
		http.Error(w, "lookup failed", http.StatusInternalServerError)
		return
	}
	if t.Status != models.TopicStatusSignupOpen {
		http.Error(w, "signup window not open (status="+string(t.Status)+")", http.StatusConflict)
		return
	}
	now := time.Now()
	if now.Before(t.SignupOpenAt) {
		http.Error(w, "signup not yet open", http.StatusConflict)
		return
	}
	if now.After(t.SignupCloseAt) {
		http.Error(w, "signup closed", http.StatusConflict)
		return
	}

	var body signupBody
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		http.Error(w, "bad body", http.StatusBadRequest)
		return
	}
	if len(body.WillingCamps) == 0 {
		http.Error(w, "willing_camps required", http.StatusBadRequest)
		return
	}
	// Dedup the camps so a buggy plugin can't insert duplicates.
	camps := dedupCamps(body.WillingCamps)
	view, err := h.signups.Upsert(r.Context(), store.UpsertSignupInput{
		TopicID:      topicID,
		AgentID:      caller.ID,
		WillingCamps: camps,
		PreValidated: body.PreValidated,
	})
	if err != nil {
		http.Error(w, "upsert failed: "+err.Error(), http.StatusBadRequest)
		return
	}
	writeJSON(w, http.StatusCreated, view)
}

// GET /api/topics/{id}/signups — list all signups for a topic.
//
// Visible to topic creator + admins + agents. Public anonymous see
// nothing (avoid leaking who-signed-up for private topics).
func (h *SignupsHandler) List(w http.ResponseWriter, r *http.Request) {
	caller := auth.FromContext(r.Context())
	if caller.Kind == "" {
		http.Error(w, "auth required", http.StatusUnauthorized)
		return
	}
	topicID := chi.URLParam(r, "id")
	if _, err := h.topics.GetByID(r.Context(), topicID); err != nil {
		http.Error(w, "topic not found", http.StatusNotFound)
		return
	}
	rows, err := h.signups.ListByTopic(r.Context(), topicID)
	if err != nil {
		http.Error(w, "list failed", http.StatusInternalServerError)
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"signups": rows, "count": len(rows)})
}

func dedupCamps(in []models.Camp) []models.Camp {
	seen := map[models.Camp]struct{}{}
	out := make([]models.Camp, 0, len(in))
	for _, c := range in {
		if _, ok := seen[c]; ok {
			continue
		}
		seen[c] = struct{}{}
		out = append(out, c)
	}
	return out
}