import React, { useState, useRef } from "react";

/**
 * CropGuard.jsx — React frontend for the crop disease detection system.
 * Implements the four-step farmer flow from §3.10.4:
 *   home -> preview -> loading -> result
 * Talks to the FastAPI backend's POST /predict endpoint.
 *
 * Set the API base URL via Vite env: VITE_API_URL=http://localhost:8000
 */

const API = import.meta.env.VITE_API_URL || "http://localhost:8000";

const SEVERITY = {
  early:    { label: "Early stage",    urgency: "Routine",   color: "#3fa34d",
              desc: "Symptoms are small and localised. You have time, but act soon." },
  moderate: { label: "Moderate stage", urgency: "Urgent",    color: "#e9a625",
              desc: "The disease covers a good part of the leaf and may spread fast. Treat this week." },
  severe:   { label: "Severe stage",   urgency: "Emergency", color: "#cf3b2f",
              desc: "Most of the leaf or plant is affected. Act today to save the rest of your crop." },
};

export default function CropGuard() {
  const [screen, setScreen] = useState("home");   // home | preview | loading | result
  const [imgUrl, setImgUrl] = useState(null);
  const [file, setFile] = useState(null);
  const [result, setResult] = useState(null);
  const [error, setError] = useState(null);
  const camRef = useRef(null);
  const galRef = useRef(null);

  function pick(e) {
    const f = e.target.files?.[0];
    if (!f) return;
    setFile(f);
    setImgUrl(URL.createObjectURL(f));
    setScreen("preview");
    e.target.value = "";
  }

  async function analyse() {
    setScreen("loading");
    setError(null);
    try {
      const fd = new FormData();
      fd.append("file", file);
      const res = await fetch(`${API}/predict`, { method: "POST", body: fd });
      if (!res.ok) throw new Error("Server error");
      setResult(await res.json());
      setScreen("result");
    } catch (err) {
      setError("Could not reach the analysis server. Check your connection and try again.");
      setScreen("preview");
    }
  }

  function reset() { setScreen("home"); setResult(null); setImgUrl(null); setFile(null); }

  return (
    <div className="cg">
      <header className="cg-head">
        <div className="cg-logo">🌿</div>
        <div><h1>CropGuard GH</h1><span>Snap a leaf. Know the disease.</span></div>
      </header>

      {screen === "home" && (
        <section>
          <div className="cg-hero">
            <h2>Diagnose crop disease in seconds</h2>
            <p>Photograph a sick leaf and get the disease, its severity, and what to do — free.</p>
          </div>
          {error && <p className="cg-err">{error}</p>}
          <button className="cg-cta" onClick={() => camRef.current.click()}>📷 Take a photo of a leaf</button>
          <button className="cg-ghost" onClick={() => galRef.current.click()}>🖼️ Choose from gallery</button>
          <p className="cg-crops">Detects: Maize · Tomato · Cassava</p>
        </section>
      )}

      {screen === "preview" && (
        <section>
          <img className="cg-preview" src={imgUrl} alt="leaf" />
          <h3>Is this the right photo?</h3>
          <p>Make sure the diseased leaf fills the frame and is in focus.</p>
          {error && <p className="cg-err">{error}</p>}
          <div className="cg-row">
            <button className="cg-ghost" onClick={reset}>← Retake</button>
            <button className="cg-cta" onClick={analyse}>🔍 Analyse crop</button>
          </div>
        </section>
      )}

      {screen === "loading" && (
        <section className="cg-loading">
          <div className="cg-spinner" />
          <h3>Analysing the leaf…</h3>
          <p>Checking colour, spots and damage</p>
        </section>
      )}

      {screen === "result" && result && (
        <Result result={result} onReset={reset} />
      )}

      <input ref={camRef} type="file" accept="image/*" capture="environment" hidden onChange={pick} />
      <input ref={galRef} type="file" accept="image/*" hidden onChange={pick} />
    </div>
  );
}

function Result({ result, onReset }) {
  const d = result.disease || {};
  const healthy = !!d.healthy;
  const sev = !healthy && result.severity ? SEVERITY[result.severity] : null;

  return (
    <section>
      <div className={`cg-rhero ${healthy ? "ok" : "bad"}`}>
        <div className="cg-rlabel">Detected disease</div>
        <div className="cg-rname">{d.name}</div>
        <div className="cg-rcrop">🌿 {d.crop}</div>
        <div className="cg-conf">
          <span>Confidence</span><b>{Math.round(result.confidence * 100)}%</b>
        </div>
      </div>

      {!healthy && sev && (
        <div className="cg-badges">
          <div className="cg-badge">
            <small>Severity</small>
            <b style={{ color: sev.color }}>● {sev.label}</b>
          </div>
          <div className="cg-badge">
            <small>Urgency</small>
            <b style={{ color: sev.color }}>{sev.urgency}</b>
          </div>
        </div>
      )}
      {sev && <p className="cg-sevdesc">{sev.desc}</p>}

      {!healthy && (
        <div className="cg-card">
          <h4>✅ What to do now</h4>
          <ol>{(d.treatment || []).map((t, i) => <li key={i}>{t}</li>)}</ol>
          <div className="cg-products">
            {(d.products || []).map((p, i) => <span key={i}>🧪 {p}</span>)}
          </div>
        </div>
      )}

      {!healthy && (
        <div className="cg-card">
          <h4>ℹ️ About this disease</h4>
          <p>{d.cause}</p>
        </div>
      )}

      {healthy && (
        <div className="cg-card cg-ok">
          <h4>✅ No disease detected</h4>
          <p>This leaf looks healthy. Keep monitoring your field weekly.</p>
        </div>
      )}

      <p className="cg-disc">
        ⚠️ This is a diagnostic aid, not a replacement for an extension officer.
        For unusual or severe cases, consult MoFA.
      </p>
      <button className="cg-cta" onClick={onReset}>🍃 Scan another leaf</button>
    </section>
  );
}