import re
from typing import List

TIME_RE = re.compile(r'^\d{2}:\d{2}:\d{2},\d{3} --> \d{2}:\d{2}:\d{2},\d{3}$')

def parse_srt(text: str) -> List[list]:
    blocks = []
    for raw in text.strip().split("\n\n"):
        lines = raw.splitlines()
        if lines:
            blocks.append(lines)
    return blocks

def blocks_to_srt(blocks: List[list]) -> str:
    return "\n\n".join("\n".join(b) for b in blocks) + "\n"

def last_end_time_ms(blocks: List[list]) -> int | None:
    if not blocks:
        return None
    end = blocks[-1][1].split(" --> ")[1]
    hh, mm, ss_ms = end.split(":")
    ss, ms = ss_ms.split(",")
    return (int(hh)*3600 + int(mm)*60 + int(ss))*1000 + int(ms)

def validate_srt_batch(in_blocks: List[list], out_blocks: List[list], prev_last_end: int | None = None):
    """
    Returns (ok: bool, report_lines: list[str])
    """
    report, ok = [], True
    if len(in_blocks) != len(out_blocks):
        ok = False
        report.append(f"[STRUCT] Block count mismatch: in={len(in_blocks)} out={len(out_blocks)}")
    for i, (ib, ob) in enumerate(zip(in_blocks, out_blocks)):
        if len(ob) < 3:
            ok = False; report.append(f"[STRUCT] Output block too short @{i}")
            continue
        if ib[0].strip() != ob[0].strip():
            ok = False; report.append(f"[INDEX] Changed @{i}: {ib[0]} → {ob[0]}")
        if ib[1].strip() != ob[1].strip():
            ok = False; report.append(f"[TIMECODE] Changed @{i}: {ib[1]} ≠ {ob[1]}")
        if not TIME_RE.match(ob[1].strip()):
            ok = False; report.append(f"[TIMECODE] Invalid format @{i}: {ob[1]}")
        if len(ib) != len(ob):
            ok = False; report.append(f"[LINES] Line-count changed @{i}: in={len(ib)} out={len(ob)}")
    if prev_last_end and out_blocks:
        def to_ms(tc: str) -> int:
            hh, mm, ss_ms = tc.split(":"); ss, ms = ss_ms.split(",")
            return (int(hh)*3600 + int(mm)*60 + int(ss))*1000 + int(ms)
        if to_ms(out_blocks[0][1].split(" --> ")[0]) < prev_last_end:
            ok = False; report.append("[OVERLAP] First block overlaps previous batch end time.")
    return ok, report

def split_batches(blocks: List[list], approx_blocks: int = 10):
    for i in range(0, len(blocks), approx_blocks):
        yield blocks[i:i+approx_blocks]