"""Decode FBX animation curve values and compare two clips frame by frame.

Range or amplitude comparisons pair up motions that merely span the same
extents; matching the actual key values settles it.
"""
import os, struct, sys, zlib
SCALAR={"Y":2,"C":1,"I":4,"F":4,"D":8,"L":8}; ELEM={"f":4,"d":8,"l":8,"i":4,"b":1}
FMT={"f":"f","d":"d","l":"q","i":"i","b":"b"}
def curves(path):
    d=open(path,'rb').read(); u64=struct.unpack("<I",d[23:27])[0]>=7500
    N=25 if u64 else 13; out=[]
    def rp(p,want):
        t=chr(d[p]); s=p; p+=1
        if t in SCALAR: p+=SCALAR[t]; return p,None
        if t in ELEM:
            n,enc,cl=struct.unpack("<III",d[p:p+12]); p+=12
            body=cl if enc else n*ELEM[t]; raw=d[p:p+body]; p+=body
            if want and n:
                try:
                    if enc: raw=zlib.decompress(raw)
                    return p,struct.unpack("<%d%s"%(n,FMT[t]),raw[:n*ELEM[t]])
                except Exception: return p,None
            return p,None
        if t in "SR":
            ln=struct.unpack("<I",d[p:p+4])[0]; p+=4+ln; return p,None
        raise ValueError
    def rn(p):
        if u64: e,np_,pl=struct.unpack("<QQQ",d[p:p+24]); q=p+24
        else: e,np_,pl=struct.unpack("<III",d[p:p+12]); q=p+12
        if e==0 and np_==0 and pl==0: return p+N
        nl=d[q]; q+=1; nm=d[q:q+nl]; q+=nl; p=q; want=nm==b"KeyValueFloat"; v=None
        for _ in range(np_):
            p,x=rp(p,want)
            if x is not None: v=x
        if want and v: out.append(v)
        while p<e:
            if d[p:p+N]==b"\x00"*N: p+=N; break
            p=rn(p)
        return e
    p=27
    while p<len(d)-160:
        if d[p:p+N]==b"\x00"*N: break
        p=rn(p)
    return out
def same_motion(a,b,eps=1e-4):
    ca,cb=curves(a),curves(b)
    ma=[c for c in ca if max(c)-min(c)>1e-6]; mb=[c for c in cb if max(c)-min(c)>1e-6]
    if len(ma)!=len(mb): return False,"moving curves %d vs %d"%(len(ma),len(mb))
    ka=sorted(ma,key=lambda c:(len(c),c[0])); kb=sorted(mb,key=lambda c:(len(c),c[0]))
    matched=0
    for x,y in zip(ka,kb):
        n=min(len(x),len(y))
        if n and all(abs(x[i]-y[i])<eps for i in range(n)): matched+=1
    return matched==len(ka), "%d/%d curves identical frame by frame"%(matched,len(ka))
if __name__=="__main__":
    for i in range(1,len(sys.argv),2):
        a,b=sys.argv[i],sys.argv[i+1]
        ok,msg=same_motion(a,b)
        print("  %-26s vs %-26s  %s  (%s)"%(os.path.basename(a),os.path.basename(b),
              "same motion" if ok else "different", msg))