"""WEM <-> Ogg Vorbis conversion using the game's codebook library."""
from .codebooks import CodebookLibrary
from .ogg import OggWriter
from .wem import Wem
from .wwvorbis import (W2V, transcode_setup, build_id_header, build_comment_header,
                       ww_packet_to_vorbis)

_LIB = None


def library() -> CodebookLibrary:
    global _LIB
    if _LIB is None:
        _LIB = CodebookLibrary()
    return _LIB


def packet_samples(blockflags, bs0, bs1):
    """Samples produced by each packet (Vorbis overlap-add rule)."""
    out = []
    prev = None
    for bf in blockflags:
        cur = bs1 if bf else bs0
        out.append(0 if prev is None else (prev // 4 + cur // 4))
        prev = cur
    return out


def wem_to_ogg(wem: Wem):
    """Returns (ogg_bytes, details dict)."""
    lib = library()
    v = wem.vorb
    setup, info = transcode_setup(wem.setup_packet(), W2V, wem.channels, lib)
    pkts, end = wem.audio_packets()
    out_pkts = []
    flags = []
    prev_bf = 0
    for i, (_, p) in enumerate(pkts):
        nxt = pkts[i + 1][1][0] if i + 1 < len(pkts) else None
        op, bf = ww_packet_to_vorbis(p, nxt, info, prev_bf, v["bs0_exp"] != v["bs1_exp"])
        out_pkts.append(op)
        flags.append(bf)
        prev_bf = bf
    bs0, bs1 = 1 << v["bs0_exp"], 1 << v["bs1_exp"]
    samples = packet_samples(flags, bs0, bs1)
    ow = OggWriter()
    ow.page([build_id_header(wem.channels, wem.rate, v["bs0_exp"], v["bs1_exp"])], 0, bos=True)
    ow.page([build_comment_header(), setup], 0)
    g = 0
    total = v["total_frames"]
    for i, op in enumerate(out_pkts):
        g += samples[i]
        last = i == len(out_pkts) - 1
        ow.page([op], min(g, total) if last else g, eos=last)
    return ow.bytes(), dict(info=info, flags=flags, samples=samples, packets=pkts, data_end=end,
                            sum_samples=sum(samples))