"""atproto firehose benchmarks — python (atproto SDK)

decodes a corpus of real firehose frames using the atproto SDK's public API:
Frame.from_bytes + parse_subscribe_repos_message + CAR.from_bytes.
under the hood: libipld (Rust extension via PyO3) for CBOR/CAR,
Python layer wraps results into typed models.

CAR.from_bytes() already decodes every block as DAG-CBOR (via libipld),
so iterating car.blocks gives us the decoded dicts directly.
"""

import statistics
import struct
import time
from dataclasses import dataclass
from pathlib import Path

from atproto import CAR, firehose_models, parse_subscribe_repos_message

WARMUP_PASSES = 2
MEASURED_PASSES = 5
FIXTURES_DIR = Path(__file__).parent.parent / "fixtures"


@dataclass
class CorpusInfo:
    frames: list[bytes]
    total_bytes: int
    min_frame: int
    max_frame: int


@dataclass
class DecodeResult:
    blocks: int
    errors: int


@dataclass
class PassResult:
    frames: int
    blocks: int
    errors: int
    elapsed_ns: int


def load_corpus(name: str) -> CorpusInfo:
    path = FIXTURES_DIR / name
    if not path.exists():
        print(f"cannot open {path}")
        print("run `just capture` first to generate fixtures")
        raise FileNotFoundError(path)

    data = path.read_bytes()
    if len(data) < 4:
        raise ValueError("corpus file too small")

    (frame_count,) = struct.unpack(">I", data[0:4])
    frames: list[bytes] = []
    pos = 4
    total_bytes = 0
    min_frame = float("inf")
    max_frame = 0

    for _ in range(frame_count):
        if pos + 4 > len(data):
            raise ValueError("truncated corpus")
        (frame_len,) = struct.unpack(">I", data[pos : pos + 4])
        pos += 4
        if pos + frame_len > len(data):
            raise ValueError("truncated corpus")
        frames.append(data[pos : pos + frame_len])
        pos += frame_len
        total_bytes += frame_len
        min_frame = min(min_frame, frame_len)
        max_frame = max(max_frame, frame_len)

    return CorpusInfo(
        frames=frames,
        total_bytes=total_bytes,
        min_frame=int(min_frame),
        max_frame=max_frame,
    )


def decode_full(frame_data: bytes) -> DecodeResult:
    """Full decode: frame parse + typed commit + CAR block extraction + per-block decode.

    Never raises — counts failures and continues.
    """
    try:
        frame = firehose_models.Frame.from_bytes(frame_data)
        msg = parse_subscribe_repos_message(frame)
    except Exception:
        return DecodeResult(blocks=0, errors=1)

    blocks = 0
    errors = 0

    if msg.blocks:
        try:
            car = CAR.from_bytes(msg.blocks)
            # CAR.from_bytes() already decodes each block as DAG-CBOR via libipld.
            # iterate to count them — the decode work has already happened.
            blocks = len(car.blocks)
        except Exception:
            errors += 1

    return DecodeResult(blocks=blocks, errors=errors)


def bench_decode(corpus: CorpusInfo) -> None:
    """Full pipeline for each frame: the real API a consumer calls."""
    for _ in range(WARMUP_PASSES):
        for frame_data in corpus.frames:
            decode_full(frame_data)

    pass_results: list[PassResult] = []

    for _ in range(MEASURED_PASSES):
        pass_blocks = 0
        pass_errors = 0
        start = time.perf_counter_ns()
        for frame_data in corpus.frames:
            result = decode_full(frame_data)
            pass_blocks += result.blocks
            pass_errors += result.errors
        elapsed_ns = time.perf_counter_ns() - start
        pass_results.append(
            PassResult(
                frames=len(corpus.frames),
                blocks=pass_blocks,
                errors=pass_errors,
                elapsed_ns=elapsed_ns,
            )
        )

    report_result("decode", corpus, pass_results)


def report_result(
    name: str, corpus: CorpusInfo, pass_results: list[PassResult]
) -> None:
    fps_values = [r.frames / (r.elapsed_ns / 1_000_000_000) for r in pass_results]
    fps_values.sort()

    total_frames = sum(r.frames for r in pass_results)
    total_blocks = sum(r.blocks for r in pass_results)
    total_errors = sum(r.errors for r in pass_results)
    total_elapsed_s = sum(r.elapsed_ns for r in pass_results) / 1_000_000_000

    total_bytes = corpus.total_bytes * MEASURED_PASSES
    throughput_mb = total_bytes / (1024 * 1024) / total_elapsed_s
    blocks_per_frame = total_blocks / total_frames

    min_fps = fps_values[0]
    median_fps = statistics.median(fps_values)
    max_fps = fps_values[-1]

    print(
        f"{name:<14} {median_fps:>10.0f} frames/sec  {throughput_mb:>8.1f} MB/s"
        f"  blocks={total_blocks} ({blocks_per_frame:.2f}/frame) errors={total_errors}"
    )
    print(
        f"{'':14} variance: min={min_fps:.0f} median={median_fps:.0f} max={max_fps:.0f} frames/sec"
    )


def main() -> None:
    print("\n=== python benchmarks ===\n")

    try:
        corpus = load_corpus("firehose-frames.bin")
    except Exception as e:
        print(f"firehose-frames.bin: SKIP ({e})")
        return

    print(f"corpus: {len(corpus.frames)} frames, {corpus.total_bytes} bytes total")
    print(f"  frame sizes: {corpus.min_frame}..{corpus.max_frame} bytes")
    print(f"  passes: {WARMUP_PASSES} warmup, {MEASURED_PASSES} measured")
    print()

    # verify first frame
    result = decode_full(corpus.frames[0])
    print(f"first frame: blocks={result.blocks} errors={result.errors}")
    print()

    bench_decode(corpus)

    print()


if __name__ == "__main__":
    main()