app.py

import gradio as gr
from transformers import pipeline

# ----------------------------
# Load TEXT detector (upgradeable)
# ----------------------------
TEXT_MODEL_ID = "wangkevin02/AI_Detect_Model"  # swap if you try another model

text_pipe = pipeline("text-classification", model=TEXT_MODEL_ID)

def _canonical(label: str) -> str | None:
    """Map raw label names to 'AI' or 'HUMAN' when possible."""
    if not label:
        return None
    l = label.strip().lower()
    # Common explicit names
    if any(k in l for k in ["ai", "machine", "generated", "fake", "synthetic", "gpt"]):
        return "AI"
    if any(k in l for k in ["human", "real", "authentic", "organic"]):
        return "HUMAN"
    # Try LABEL_X -> use id2label if present
    if l.startswith("label_"):
        try:
            idx = int(l.split("_")[-1])
        except ValueError:
            return None
        id2label = getattr(text_pipe.model.config, "id2label", None)
        if isinstance(id2label, dict) and idx in id2label:
            return _canonical(str(id2label[idx]))
    # Sometimes labels are just "0"/"1"
    if l in {"0", "1"}:
        id2label = getattr(text_pipe.model.config, "id2label", None)
        if isinstance(id2label, dict) and l.isdigit():
            mapped = id2label.get(int(l))
            if mapped:
                return _canonical(str(mapped))
    return None

def _aggregate_probs(raw_results):
    """
    Convert pipeline outputs into {'AI': p, 'HUMAN': p, 'raw': {...}} robustly.
    Ensures both keys exist and sum <= 1.0 (may be < 1 if labels don't map).
    """
    # text-classification with top_k=None returns a list of dicts
    # e.g. [{'label': 'AI', 'score': 0.82}, {'label': 'HUMAN', 'score': 0.18}]
    if isinstance(raw_results, list) and raw_results and isinstance(raw_results[0], dict):
        label_scores = {d["label"]: float(d["score"]) for d in raw_results}
    elif isinstance(raw_results, list) and raw_results and isinstance(raw_results[0], list):
        # return_all_scores=True style: [[{label, score}, {label, score}, ...]]
        label_scores = {d["label"]: float(d["score"]) for d in raw_results[0]}
    else:
        label_scores = {}

    ai_p = 0.0
    human_p = 0.0
    for lbl, sc in label_scores.items():
        canon = _canonical(lbl)
        if canon == "AI":
            ai_p += sc
        elif canon == "HUMAN":
            human_p += sc

    # If nothing mapped, fall back to top label heuristic
    if ai_p == 0.0 and human_p == 0.0 and label_scores:
        top_lbl = max(label_scores, key=label_scores.get)
        top_sc = label_scores[top_lbl]
        canon = _canonical(top_lbl)
        if canon == "AI":
            ai_p = top_sc
            human_p = 1.0 - top_sc
        elif canon == "HUMAN":
            human_p = top_sc
            ai_p = 1.0 - top_sc

    return {"AI": round(ai_p, 6), "HUMAN": round(human_p, 6), "raw": label_scores}

def _verdict(ai_p: float, human_p: float, n_words: int) -> str:
    conf = max(ai_p, human_p)
    if n_words < 120:
        band = "LOW (short text)"
    elif conf < 0.60:
        band = "LOW (uncertain)"
    elif conf < 0.80:
        band = "MEDIUM"
    else:
        band = "HIGH"

    if ai_p > human_p:
        return f"🤖 Likely AI — Confidence: {band}"
    elif human_p > ai_p:
        return f"📝 Likely Human — Confidence: {band}"
    else:
        return "❓ Uncertain — Confidence: LOW"

def detect_text(input_text: str):
    text = (input_text or "").strip()
    if not text:
        return {}, "❌ Please enter some text."

    try:
        # Get ALL label scores so we can map correctly
        results = text_pipe(text, top_k=None)
        agg = _aggregate_probs(results)
        ai_p, human_p = float(agg["AI"]), float(agg["HUMAN"])

        # Normalize to show nicely, but keep raw too
        probs_out = {
            "AI-generated": round(ai_p, 4),
            "Human-written": round(human_p, 4),
        }
        # Optional: include raw labels so you can debug mappings in UI
        # probs_out.update({f"raw::{k}": round(v, 4) for k, v in agg["raw"].items()})

        verdict = _verdict(ai_p, human_p, n_words=len(text.split()))
        return probs_out, verdict

    except Exception as e:
        return {}, f"❌ Error: {str(e)}"

# ----------------------------
# (Optional) IMAGE detector — won't crash if model unavailable
# ----------------------------
try:
    from PIL import Image
    image_pipe = pipeline("image-classification", model="umm-maybe/ai-vs-human-images")
except Exception:
    image_pipe = None

def detect_image(img):
    if image_pipe is None:
        return {}, "⚠️ Image detector not available on this Space."
    try:
        results = image_pipe(img)
        label_scores = {d["label"]: float(d["score"]) for d in results}
        best = max(label_scores, key=label_scores.get)
        if any(k in best.lower() for k in ["ai", "fake", "generated", "synthetic"]):
            return label_scores, "🤖 This image looks AI-generated"
        else:
            return label_scores, "📷 This image looks Human/Real"
    except Exception as e:
        return {}, f"❌ Error: {str(e)}"

# ----------------------------
# UI
# ----------------------------
with gr.Blocks() as demo:
    gr.Markdown("# 🔍 AI Content Detector\nDetect whether **text** (and optionally images) are AI-generated or human-made.")

    with gr.Tab("📝 Text"):
        txt = gr.Textbox(label="Enter text", lines=10, placeholder="Paste text here…")
        out_probs = gr.Label(label="Probabilities")
        out_verdict = gr.Textbox(label="Verdict", interactive=False)
        btn = gr.Button("Analyze", variant="primary")
        btn.click(detect_text, inputs=txt, outputs=[out_probs, out_verdict])

    with gr.Tab("📷 Image"):
        img_in = gr.Image(type="pil", label="Upload an image")
        img_probs = gr.Label(label="Probabilities")
        img_verdict = gr.Textbox(label="Verdict", interactive=False)
        btn2 = gr.Button("Analyze Image")
        btn2.click(detect_image, inputs=img_in, outputs=[img_probs, img_verdict])

if __name__ == "__main__":
    demo.launch()