"""
MT5 `.hcc` history decoder (broker M1 bars), rebuilt 2026-09-27.

Layout (measured on FivePercentOnline-Real SP500 2024):
  * 228-byte file header (UTF-16 copyright string)
  * index from byte 228: 18-byte records (u32 idx, u32 update time, u16 ?,
    u32 chunk size, u32 ABSOLUTE chunk offset), one per day, newest first
  * each chunk: 129-byte header (u16 = 129, UTF-16 symbol name, ...), then
    N x 60-byte MqlRates (i64 time, 4 x f64 OHLC, i64 tick_volume, i32 spread,
    i64 real_volume)
  * the first record of a chunk is often a DAILY SUMMARY (time 00:00, tick
    volume = the day's total) - dropped when its tick volume is >= 90% of the
    rest of the chunk, or when it is not strictly before the next bar.

Times are the broker clock. Real volume is 0 on CFDs; spread is in points.
"""

from __future__ import annotations

import glob
import os
import struct

import numpy as np

REC = np.dtype([("t", "<i8"), ("o", "<f8"), ("h", "<f8"), ("l", "<f8"), ("c", "<f8"),
                ("tv", "<i8"), ("sp", "<i4"), ("rv", "<i8")])
assert REC.itemsize == 60


def read_hcc(path: str) -> np.ndarray:
    b = open(path, "rb").read()
    chunks = []
    k = 0
    while 228 + 18 * (k + 1) <= len(b):
        _, _, _, size, off = struct.unpack_from("<IIHII", b, 228 + 18 * k)
        if off < 228 or off + size > len(b) or size < 129:
            break
        hdr = struct.unpack_from("<H", b, off)[0]
        body = size - hdr
        if hdr == 129 and body > 0 and body % 60 == 0:
            a = np.frombuffer(b, REC, body // 60, off + hdr).copy()
            if len(a) > 1 and (a["tv"][0] >= 0.9 * a["tv"][1:].sum() or a["t"][0] >= a["t"][1]):
                a = a[1:]
            chunks.append(a)
        k += 1
    if not chunks:
        return np.zeros(0, REC)
    a = np.concatenate(chunks)
    a = a[np.argsort(a["t"], kind="stable")]
    keep = np.concatenate([[True], np.diff(a["t"]) > 0])
    return a[keep]


def load_m1(folder: str, years=None) -> np.ndarray:
    files = sorted(glob.glob(os.path.join(folder, "*.hcc")))
    if years is not None:
        files = [f for f in files if int(os.path.basename(f)[:4]) in years]
    a = np.concatenate([read_hcc(f) for f in files])
    a = a[np.argsort(a["t"], kind="stable")]
    a = a[np.concatenate([[True], np.diff(a["t"]) > 0])]
    step = np.diff(a["t"])
    return a, step