#!/usr/bin/env python3
"""Rough STPC walk (boundaries only): models, animsets, flag-0x100 block, then strat code.
Reimplemented from FUN_0042ab50 / FUN_0041f770 / FUN_0041f8b0 (groove.exe)."""
import struct


def u32(d, o):
    return struct.unpack_from('<I', d, o)[0]


def u16(d, o):
    return struct.unpack_from('<H', d, o)[0]


def models(d, o, n):
    hdr = o
    o += n * 0x8c
    out = []
    for i in range(n):
        h = hdr + i * 0x8c
        start = o
        o += u16(d, h + 0x86) * 2
        o += u16(d, h + 0x6c) * 0x18
        o += u16(d, h + 0x6e) * 0x1c
        o += (u16(d, h + 0x78) + u16(d, h + 0x7a) + u16(d, h + 0x7c)) * 0x20
        out.append((h, start, o))
    return o, out


def animsets(d, o, n):
    hdr = o
    o += n * 0x20
    for i in range(n):
        h = hdr + i * 0x20
        a0, a1, nfr, a3, a4, a5, a6, a7 = struct.unpack_from('<8I', d, h)
        o += a0 * 4
        if a3 == 0:
            o += nfr * 8
        if a4:
            o += nfr * 4
        o += nfr * 4
        for f in range(nfr):
            if a4:
                if f == 0:
                    o += a4 * 8
                else:
                    o += a4 * 2 + (2 if a4 & 1 else 0)
            o += a6 * 0x40
    return o


def walk(d, wfpc):
    n = u32(d, 0)
    o, mdl = 4, []
    for _ in range(n):          # FUN_0041f770(&p,1,..) per model: header directly followed by data
        o, mm = models(d, o, 1)
        mdl += mm
    na = u32(d, o); o += 4
    for _ in range(na):         # FUN_0041f8b0(&p,1,..) per animset
        o = animsets(d, o, 1)
    extra = []
    if wfpc & 0x100:
        n3 = u32(d, o); o += 4
        for _ in range(n3):
            h = o
            cnt = u32(d, h + 4)
            o = h + 16
            if cnt & 0x1fffffff:
                o += cnt * 8
            o, mm = models(d, o, cnt)
            extra.append((h, cnt, mm))
    return dict(models=mdl, nanim=na, extra=extra, code=o)