import numpy as np
from struct import pack, unpack


"""
Reads PC2 files, and proposed format PC16 files
Inputs:
- file: path to .pc2/.pc16 file
- float16: False for PC2 files, True for PC16
Output:
- data: dictionary with .pc2/.pc16 file data
NOTE: 16-bit floats lose precision with high values (positive or negative),
	  we do not recommend using this format for data outside range [-2, 2]
"""
def readPC2(file, float16=False):
	assert file.endswith('.pc2') and not float16 or file.endswith('.pc16') and float16, 'File format not consistent with specified input format'
	data = {}
	bytes = 2 if float16 else 4
	dtype = np.float16 if float16 else np.float32
	with open(file, 'rb') as f:
		# Header
		data['sign'] = f.read(12)
		# data['version'] = int.from_bytes(f.read(4), 'little')
		data['version'] = unpack('<i', f.read(4))[0]
		# Num points
		# data['nPoints'] = int.from_bytes(f.read(4), 'little')
		data['nPoints'] = unpack('<i', f.read(4))[0]
		# Start frame
		data['startFrame'] = unpack('f', f.read(4))
		# Sample rate
		data['sampleRate'] = unpack('f', f.read(4))
		# Number of samples
		# data['nSamples'] = int.from_bytes(f.read(4), 'little')
		data['nSamples'] = unpack('<i', f.read(4))[0]
		# Animation data
		size = data['nPoints']*data['nSamples']*3*bytes
		data['V'] = np.frombuffer(f.read(size), dtype=dtype).astype(np.float32)
		data['V'] = data['V'].reshape(data['nSamples'], data['nPoints'], 3)
		
	return data
	
"""
Reads an specific frame of PC2/PC16 files
Inputs:
- file: path to .pc2/.pc16 file
- frame: number of the frame to read
- float16: False for PC2 files, True for PC16
Output:
- T: mesh vertex data at specified frame
"""
def readPC2Frame(file, frame, float16=False):
	assert file.endswith('.pc2') and not float16 or file.endswith('.pc16') and float16, 'File format not consistent with specified input format'
	assert frame >= 0 and isinstance(frame,int), 'Frame must be a positive integer'
	bytes = 2 if float16 else 4
	dtype = np.float16 if float16 else np.float32
	with open(file,'rb') as f:
		# Num points
		f.seek(16)
		# nPoints = int.from_bytes(f.read(4), 'little')
		nPoints = unpack('<i', f.read(4))[0]
		# Number of samples
		f.seek(28)
		# nSamples = int.from_bytes(f.read(4), 'little')
		nSamples = unpack('<i', f.read(4))[0]
		if frame > nSamples:
			print("Frame index outside size")
			print("\tN. frame: " + str(frame))
			print("\tN. samples: " + str(nSamples))
			return
		# Read frame
		size = nPoints * 3 * bytes
		f.seek(size * frame, 1) # offset from current '1'
		T = np.frombuffer(f.read(size), dtype=dtype).astype(np.float32)
	return T.reshape(nPoints, 3)

"""
Writes PC2 and PC16 files
Inputs:
- file: path to file (overwrites if exists)
- V: 3D animation data as a three dimensional array (N. Frames x N. Vertices x 3)
- float16: False for writing as PC2 file, True for PC16
This function assumes 'startFrame' to be 0 and 'sampleRate' to be 1
NOTE: 16-bit floats lose precision with high values (positive or negative),
	  we do not recommend using this format for data outside range [-2, 2]
"""
def writePC2(file, V, float16=False):
	assert file.endswith('.pc2') and not float16 or file.endswith('.pc16') and float16, 'File format not consistent with specified input format'
	if float16: V = V.astype(np.float16)
	else: V = V.astype(np.float32)
	with open(file, 'wb') as f:
		# Create the header
		headerFormat='<12siiffi'
		headerStr = pack(headerFormat, b'POINTCACHE2\0',
						1, V.shape[1], 0, 1, V.shape[0])
		f.write(headerStr)
		# Write vertices
		f.write(V.tobytes())

"""
Reads OBJ files
Only handles vertices, faces and UV maps
Input:
- file: path to .obj file
Outputs:
- V: 3D vertices
- F: 3D faces
- Vt: UV vertices
- Ft: UV faces
Correspondence between mesh and UV map is implicit in F to Ft correspondences
If no UV map data in .obj file, it shall return Vt=None and Ft=None
"""
def readOBJ(file):
	V, Vt, F, Ft = [], [], [], []
	with open(file, 'r') as f:
		T = f.readlines()
	for t in T:
		# 3D vertex
		if t.startswith('v '):
			v = [float(n) for n in t.replace('v ','').split(' ')]
			V += [v]
		# UV vertex
		elif t.startswith('vt '):
			v = [float(n) for n in t.replace('vt ','').split(' ')]
			Vt += [v]
		# Face
		elif t.startswith('f '):
			idx = [n.split('/') for n in t.replace('f ','').split(' ')]
			f = [int(n[0]) - 1 for n in idx]
			F += [f]
			# UV face
			if '/' in t:
				f = [int(n[1]) - 1 for n in idx]
				Ft += [f]
	V = np.array(V, np.float32)
	Vt = np.array(Vt, np.float32)
	if Ft: assert len(F) == len(Ft), 'Inconsistent .obj file, mesh and UV map do not have the same number of faces' 
	else: Vt, Ft = None, None
	return V, F, Vt, Ft



"""
Writes OBJ files
Only handles vertices, faces and UV maps
Inputs:
- file: path to .obj file (overwrites if exists)
- V: 3D vertices
- F: 3D faces
- Vt: UV vertices
- Ft: UV faces
Correspondence between mesh and UV map is implicit in F to Ft correspondences
If no UV map data as input, it will write only 3D data in .obj file
"""
def writeOBJ(file, V, F, Vt=None, Ft=None):
	if not Vt is None:
		assert len(F) == len(Ft), 'Inconsistent data, mesh and UV map do not have the same number of faces'
		
	with open(file, 'w') as file:
		# Vertices
		for v in V:
			line = 'v ' + ' '.join([str(_) for _ in v]) + '\n'
			file.write(line)
		# UV verts
		if not Vt is None:
			for v in Vt:
				line = 'vt ' + ' '.join([str(_) for _ in v]) + '\n'
				file.write(line)
		# 3D Faces / UV faces
		if Ft:
			F = [[str(i+1)+'/'+str(j+1) for i,j in zip(f,ft)] for f,ft in zip(F,Ft)]
		else:
			F = [[str(i + 1) for i in f] for f in F]		
		for f in F:
			line = 'f ' + ' '.join(f) + '\n'
			file.write(line)