#!/usr/bin/env python3
"""Build HDTF id-paired subset csvs for Protocol 4.

Logic (from user's paper):
  * The FairTalking-Bench Real pool is drawn from CelebV-HQ + DFDC + HDTF.
  * HDTF videos that ended up in the main train.csv  -> Subset A (training IDs)
  * HDTF videos that ended up in the main test.csv   -> Subset B (testing IDs)
  * HDTF IDs that were NEVER included in FairTalking -> Subset C (unseen IDs)
    (also includes HDTF videos that went into val.csv — anything not in train)

For every Real HDTF video with basename_num XXXX we check that
  <root>/<gen>/XXXX_Fake_<gen>.mp4
exists for all 8 generators; rows where any generator is missing are skipped.

For Subset C we need an external list of HDTF identities not in the csv.
If --external_hdtf_ids <txt> is given, those IDs are treated as subset C.
Otherwise subset C is left empty and you fill it in later.

Output csvs have columns:
    identity_id, basename_num, subset, source
and are written to $DATA_ROOT/hdtf_subset_{a,b,c}.csv.
"""
from __future__ import annotations

import argparse
import sys
from pathlib import Path

import pandas as pd


GENERATORS = (
    "AniPortrait", "Ditto", "EDTalk", "Float",
    "Hallo", "Joyvasa", "SadTalk", "Sonic",
)


def load_split(root: Path, csv_name: str) -> pd.DataFrame:
    df = pd.read_csv(root / csv_name)
    df["_num"] = df["basename"].str.extract(r"^(\d+)_")[0]
    df["_kind"] = df["basename"].str.extract(r"_(Real|Fake)$")[0]
    return df


def hdtf_real_rows(df: pd.DataFrame) -> pd.DataFrame:
    # real rows from HDTF — identified by source column when present, else heuristic
    real = df[df["_kind"] == "Real"].copy()
    if "source" in real.columns:
        # the paper's real pool column may say "real"; actual dataset tag is
        # typically in filename suffix — try that as secondary check
        pass
    return real  # caller filters further


def fakes_exist(root: Path, num: str) -> bool:
    for g in GENERATORS:
        if not (root / g / f"{num}_Fake_{g}.mp4").exists():
            return False
    return True


def find_hdtf(real_df: pd.DataFrame, root: Path) -> pd.DataFrame:
    """Look at physical Real/ dir to find which rows have *_Real_HDTF*.mp4 suffix."""
    hdtf_nums = set()
    for p in (root / "Real").glob("*_Real_HDTF*.mp4"):
        num = p.name.split("_", 1)[0]
        hdtf_nums.add(num)
    sel = real_df[real_df["_num"].isin(hdtf_nums)].copy()
    sel["identity_id"] = sel["basename_old"].astype(str)
    sel["basename_num"] = sel["_num"]
    return sel


def main() -> None:
    ap = argparse.ArgumentParser()
    ap.add_argument("--data_root", required=True)
    ap.add_argument(
        "--external_hdtf_ids",
        default=None,
        help="txt file, one HDTF identity per line, that were never included in FairTalking — used for Subset C",
    )
    ap.add_argument("--external_hdtf_root", default=None,
                    help="if given, also verify Subset C videos exist under this path")
    args = ap.parse_args()

    root = Path(args.data_root)

    train_df = load_split(root, "train.csv")
    val_df = load_split(root, "val.csv")
    test_df = load_split(root, "test.csv")

    hdtf_train = find_hdtf(train_df, root)
    hdtf_val = find_hdtf(val_df, root)
    hdtf_test = find_hdtf(test_df, root)

    # keep only ones that have all 8 generator fakes alongside
    def _keep_with_fakes(df: pd.DataFrame) -> pd.DataFrame:
        mask = df["basename_num"].apply(lambda n: fakes_exist(root, n))
        return df[mask].copy()

    subset_a = _keep_with_fakes(hdtf_train)
    subset_b = _keep_with_fakes(hdtf_test)
    # val rows merged into B (for 'seen' identity set) OR could go their own csv;
    # paper uses A/B/C only, so we leave val as C candidates.
    subset_a["subset"] = "A"
    subset_b["subset"] = "B"

    keep_cols = ["identity_id", "basename_num", "subset", "source"]
    for c in keep_cols:
        if c not in subset_a.columns: subset_a[c] = ""
        if c not in subset_b.columns: subset_b[c] = ""

    subset_a[keep_cols].to_csv(root / "hdtf_subset_a.csv", index=False)
    subset_b[keep_cols].to_csv(root / "hdtf_subset_b.csv", index=False)
    print(f"[prepare_hdtf_splits] A (train-seen HDTF): {len(subset_a)}")
    print(f"[prepare_hdtf_splits] B (test-seen HDTF):  {len(subset_b)}")

    # Subset C: truly unseen HDTF identities.
    # If user provides a list file, build Subset C; otherwise emit an empty csv.
    subset_c = pd.DataFrame(columns=keep_cols)
    if args.external_hdtf_ids and Path(args.external_hdtf_ids).exists():
        ids = [ln.strip() for ln in open(args.external_hdtf_ids) if ln.strip()]
        rows = []
        # external HDTF videos don't have fakes in FairTalking-Bench;
        # for Subset C eval we generally use only the RIGHT side (real videos)
        # for identity-feature extraction. Fake side comes from inference, not from disk.
        for i, ident in enumerate(ids):
            rows.append({
                "identity_id": ident,
                "basename_num": f"EXT{i:04d}",
                "subset": "C",
                "source": "external_hdtf",
            })
        subset_c = pd.DataFrame(rows, columns=keep_cols)
    subset_c.to_csv(root / "hdtf_subset_c.csv", index=False)
    print(f"[prepare_hdtf_splits] C (unseen HDTF):     {len(subset_c)}")

    # tiny manifest for debugging
    manifest = {
        "train_total": len(train_df),
        "val_total": len(val_df),
        "test_total": len(test_df),
        "hdtf_train": len(hdtf_train),
        "hdtf_val": len(hdtf_val),
        "hdtf_test": len(hdtf_test),
        "subset_a": len(subset_a),
        "subset_b": len(subset_b),
        "subset_c": len(subset_c),
    }
    print(f"[prepare_hdtf_splits] manifest: {manifest}")


if __name__ == "__main__":
    main()