"use client";

import { useEffect, useState, useCallback } from "react";
import { useRouter } from "next/navigation";
import { AuthGuard } from "@/components/auth/AuthGuard";
import { Navbar } from "@/components/layout/Navbar";
import { BottomNav } from "@/components/layout/BottomNav";
import { WeeklyPlanGrid } from "@/components/plans/WeeklyPlanGrid";
import { WeekPicker } from "@/components/plans/WeekPicker";
import { Button } from "@/components/ui/Button";
import { Spinner } from "@/components/ui/Spinner";
import { api } from "@/lib/api";
import type { GeneratedWeeklyPlan, WeeklyPreview } from "@/lib/types";

function getCurrentMonday(): string {
  const now = new Date();
  const day = now.getDay();
  const diff = day === 0 ? -6 : 1 - day;
  const monday = new Date(now);
  monday.setDate(now.getDate() + diff);
  const yyyy = monday.getFullYear();
  const mm = String(monday.getMonth() + 1).padStart(2, "0");
  const dd = String(monday.getDate()).padStart(2, "0");
  return `${yyyy}-${mm}-${dd}`;
}

export default function DashboardPage() {
  const router = useRouter();
  const [selectedMonday, setSelectedMonday] = useState(getCurrentMonday);
  const [plans, setPlans] = useState<GeneratedWeeklyPlan[]>([]);
  const [preview, setPreview] = useState<WeeklyPreview | null>(null);
  const [loading, setLoading] = useState(true);
  const [generating, setGenerating] = useState(false);
  const [saving, setSaving] = useState(false);
  const [confirming, setConfirming] = useState(false);
  const [error, setError] = useState("");

  const fetchPlans = useCallback(async () => {
    try {
      try {
        const prefs = await api.getPreferences();
        const hasPrefs =
          prefs.available_equipment.length > 0 ||
          prefs.preferred_workout_types.length > 0 ||
          prefs.target_muscle_groups.length > 0;
        if (!hasPrefs) {
          router.replace("/onboarding");
          return;
        }
      } catch {
        router.replace("/onboarding");
        return;
      }

      const data = await api.getPlans();
      setPlans(data);
    } catch (err) {
      console.error("Failed to fetch plans:", err);
    } finally {
      setLoading(false);
    }
  }, [router]);

  useEffect(() => {
    fetchPlans();
  }, [fetchPlans]);

  // Clear preview when week changes
  useEffect(() => {
    setPreview(null);
  }, [selectedMonday]);

  const savedPlan = plans.find((p) => p.week_start_date === selectedMonday);

  const handleGenerate = async () => {
    setGenerating(true);
    setError("");
    try {
      const data = await api.previewPlan(selectedMonday);
      setPreview(data);
    } catch (err) {
      const msg =
        err instanceof Error ? err.message : "Failed to generate preview";
      setError(msg);
      console.error("Failed to generate preview:", err);
    } finally {
      setGenerating(false);
    }
  };

  const handleConfirm = async () => {
    if (!savedPlan) return;
    setConfirming(true);
    setError("");
    try {
      await api.confirmPlan(savedPlan.id);
      await fetchPlans();
    } catch (err) {
      const msg = err instanceof Error ? err.message : "Failed to confirm plan";
      setError(msg);
    } finally {
      setConfirming(false);
    }
  };

  const handleSave = async () => {
    if (!preview) return;
    setSaving(true);
    setError("");
    try {
      await api.savePlan(preview);
      setPreview(null);
      await fetchPlans();
    } catch (err) {
      const msg = err instanceof Error ? err.message : "Failed to save plan";
      setError(msg);
      console.error("Failed to save plan:", err);
    } finally {
      setSaving(false);
    }
  };

  return (
    <AuthGuard>
      <Navbar />
      <BottomNav />
      <main className="pt-20 pb-20 px-4 max-w-5xl mx-auto">
        <div className="flex items-center justify-between mb-6">
          <h1 className="text-2xl font-bold text-zinc-100">Dashboard</h1>
          <WeekPicker
            selectedMonday={selectedMonday}
            onChange={setSelectedMonday}
          />
        </div>

        {error && (
          <div className="mb-4 p-3 rounded-lg bg-red-500/10 border border-red-500/20 text-red-400 text-sm">
            {error}
          </div>
        )}

        {preview?.warnings && preview.warnings.length > 0 && (
          <div className="mb-4 p-3 rounded-lg bg-yellow-500/10 border border-yellow-500/20 text-yellow-300 text-sm">
            <div className="font-medium mb-1">Heads up</div>
            <ul className="list-disc list-inside space-y-0.5">
              {preview.warnings.map((w, i) => (
                <li key={i}>{w}</li>
              ))}
            </ul>
          </div>
        )}

        {loading ? (
          <div className="flex items-center justify-center py-20">
            <Spinner size="lg" />
          </div>
        ) : preview ? (
          /* ===== Preview mode ===== */
          <div>
            <div className="flex items-center justify-between mb-6">
              <h2 className="text-lg font-semibold text-zinc-200">
                Preview
              </h2>
              <div className="flex gap-2">
                <Button
                  variant="ghost"
                  size="sm"
                  onClick={() => setPreview(null)}
                >
                  Discard
                </Button>
                <Button
                  variant="secondary"
                  size="sm"
                  loading={generating}
                  onClick={handleGenerate}
                >
                  Regenerate
                </Button>
                <Button
                  variant="primary"
                  size="sm"
                  loading={saving}
                  onClick={handleSave}
                >
                  Save Plan
                </Button>
              </div>
            </div>
            <WeeklyPlanGrid
              preview={preview}
              onPreviewChange={setPreview}
            />
          </div>
        ) : savedPlan ? (
          /* ===== Saved plan mode ===== */
          <div>
            <div className="flex items-center justify-between mb-6">
              <h2 className="text-lg font-semibold text-zinc-200">
                This Week&apos;s Plan
              </h2>
              <div className="flex gap-2">
                {savedPlan.generated_workouts.some(
                  (w) => !w.is_rest_day && w.status === "pending"
                ) && (
                  <Button
                    variant="primary"
                    size="sm"
                    loading={confirming}
                    onClick={handleConfirm}
                  >
                    Save to Calendar
                  </Button>
                )}
                <Button
                  variant="secondary"
                  size="sm"
                  loading={generating}
                  onClick={handleGenerate}
                >
                  Regenerate
                </Button>
              </div>
            </div>
            <WeeklyPlanGrid plan={savedPlan} onUpdate={fetchPlans} />
          </div>
        ) : (
          /* ===== No plan ===== */
          <div className="flex flex-col items-center justify-center py-20 gap-6">
            <p className="text-zinc-400 text-lg text-center">
              No plan for this week yet. Let&apos;s get started!
            </p>
            <Button
              variant="primary"
              size="lg"
              loading={generating}
              onClick={handleGenerate}
            >
              Generate Plan
            </Button>
          </div>
        )}
      </main>
    </AuthGuard>
  );
}