#!/usr/bin/env python3
import argparse
import json
from collections import Counter
from pathlib import Path

import numpy as np


def parse_args():
    p = argparse.ArgumentParser(description="Extract per-expert windows from a continuous GPT-OSS trace")
    p.add_argument("--run-dir", required=True)
    p.add_argument("--output-root", required=True)
    p.add_argument("--layer-idx", type=int, default=0)
    p.add_argument("--phase", default="decode")
    p.add_argument("--trace-domain", choices=["raw", "resampled"], default="resampled")
    p.add_argument("--pad-before", type=int, default=0, help="padding in resampled samples")
    p.add_argument("--pad-after", type=int, default=0, help="padding in resampled samples")
    p.add_argument("--min-samples", type=int, default=16)
    return p.parse_args()


def raw_to_resampled_start(raw_idx: int, raw_len: int, resampled_len: int) -> int:
    if raw_len <= 1 or resampled_len <= 1:
        return 0
    return int(np.floor(float(raw_idx) * float(resampled_len - 1) / float(raw_len - 1)))


def raw_to_resampled_end(raw_idx: int, raw_len: int, resampled_len: int) -> int:
    if raw_len <= 1 or resampled_len <= 1:
        return 1
    return int(np.ceil(float(raw_idx) * float(resampled_len - 1) / float(raw_len - 1)))


def main():
    args = parse_args()
    run_dir = Path(args.run_dir).expanduser().resolve()
    output_root = Path(args.output_root).expanduser().resolve()
    output_root.mkdir(parents=True, exist_ok=True)

    meta = json.loads((run_dir / "capture_meta.json").read_text())
    timeline = json.loads((run_dir / "timeline.json").read_text())
    trace_path = run_dir / ("trace.npy" if str(args.trace_domain) == "raw" else "trace_resampled.npy")
    trace = np.load(trace_path, mmap_mode="r")

    raw_len = int(meta["raw_trace_len"])
    trace_len = int(trace.shape[0])

    starts = {}
    counts = Counter()
    durations = []
    records = []

    for ev in timeline:
        if str(ev.get("phase", "")) != str(args.phase):
            continue
        layer_val = ev.get("layer_idx")
        if layer_val is None:
            continue
        if int(layer_val) != int(args.layer_idx):
            continue

        name = str(ev.get("name"))
        if name == "expert_start":
            key = (int(ev["decode_step_idx"]), int(ev["expert_idx"]))
            starts[key] = int(ev["trace_sample_index"])
            continue

        if name != "expert_end":
            continue

        key = (int(ev["decode_step_idx"]), int(ev["expert_idx"]))
        if key not in starts:
            continue

        start_raw = int(starts.pop(key))
        end_raw = int(ev["trace_sample_index"])
        if str(args.trace_domain) == "raw":
            start = max(0, int(start_raw) - int(args.pad_before))
            end = min(trace_len, int(end_raw) + int(args.pad_after))
        else:
            start = max(0, raw_to_resampled_start(start_raw, raw_len, trace_len) - int(args.pad_before))
            end = min(trace_len, raw_to_resampled_end(end_raw, raw_len, trace_len) + int(args.pad_after))
        if end - start < int(args.min_samples):
            continue

        decode_step_idx, expert_idx = key
        seg = np.asarray(trace[start:end], dtype=np.float32)
        class_dir = output_root / f"expert_{expert_idx:02d}"
        class_dir.mkdir(parents=True, exist_ok=True)
        out_path = class_dir / f"step_{decode_step_idx:05d}.npy"
        np.save(out_path, seg)

        counts[expert_idx] += 1
        durations.append(int(end - start))
        records.append(
            {
                "phase": str(args.phase),
                "layer_idx": int(args.layer_idx),
                "decode_step_idx": int(decode_step_idx),
                "expert_idx": int(expert_idx),
                "start_raw": int(start_raw),
                "end_raw": int(end_raw),
                "start_resampled": int(start),
                "end_resampled": int(end),
                "samples": int(end - start),
                "trace_file": str(out_path),
            }
        )

    summary = {
        "run_dir": str(run_dir),
        "output_root": str(output_root),
        "phase": str(args.phase),
        "layer_idx": int(args.layer_idx),
        "trace_domain": str(args.trace_domain),
        "raw_trace_len": int(raw_len),
        "trace_len": int(trace_len),
        "pad_before": int(args.pad_before),
        "pad_after": int(args.pad_after),
        "min_samples": int(args.min_samples),
        "num_segments": int(sum(counts.values())),
        "class_counts": {f"expert_{k:02d}": int(v) for k, v in sorted(counts.items())},
        "duration_mean": None if not durations else float(np.mean(durations)),
        "duration_median": None if not durations else float(np.median(durations)),
        "duration_min": None if not durations else int(np.min(durations)),
        "duration_max": None if not durations else int(np.max(durations)),
    }
    (output_root / "extract_summary.json").write_text(json.dumps(summary, indent=2))
    with (output_root / "extract_records.jsonl").open("w") as f:
        for rec in records:
            f.write(json.dumps(rec) + "\n")
    print(json.dumps(summary, indent=2))


if __name__ == "__main__":
    main()