import bpy
import math
from mathutils import Vector


def debug_dump(k, particle):
    hk = particle.hair_keys[k]
    return "%s\t%s\t%s\t%s\n%s" % (hk.co_local, hk.co,
                               particle.prev_location, particle.location,
                                   (hk.co - particle.prev_location))


def comb1(obj):
    ps = obj.particle_systems[0]
    dx =10
    dy = 10
    for i in range(dx):
        for j in range(dy):
            idx = i*10+j
            particle = ps.particles[idx]
            dz = len(particle.hair_keys)
            loc = ( (i/dx-0.5)* 7, (j/dy-0.5)*7, 0)
            particle.hair_keys[0].co_local = (0,0,0)
            loc = particle.hair_keys[0].co
            particle.location = loc
            particle.prev_location = loc
            for k in range(dz):
                print(particle.hair_keys[k].co_local)
                x =  k*0.1*i
                r = math.pi*dy/(1+j+1)
                theta = k /r
                y =  (1-math.cos(theta))*r
                z = math.sin(theta)*r
                particle.hair_keys[k].co_local = (x,y,z)
                print(debug_dump(k, particle))
          #      particle.hair_keys[k].co = particle.location + Vector( [x,y,z] )
          #      print(debug_dump(k, particle))
                #particle.hair_keys[k].co_local = (x,y,z)
                #print(debug_dump(k, particle))

def bary(verts, w):
    rval = verts[0]*w[0]
    for i in range(1,len(verts)):
        rval = rval + verts[i]*w[i]
    return rval


def bary2(obj, particle):
    mesh = obj.data
    fuv = particle.fuv
    return bary([mesh.vertices[i].co for i in mesh.polygons[0].vertices], fuv)


def comb2(obj):
    ps = obj.particle_systems[0]

    for p in ps.particles:
        p.fuv = [0.1, 0.9,0,0]
        p.location = bary2(obj, p)

    dx =5
    dy = 5
    for i in range(dx):
        for j in range(dy):
            idx = i*dx+j
            particle = ps.particles[idx]
            dz = len(particle.hair_keys)
            # this next bit does not work unless your blender has hacked DNA.  The fuv property is not normally available
            uv = [ i / (dx-1) , j/(dy-1)]
            particle.fuv = (uv[0]*uv[1], (1-uv[0])*uv[1], (1-uv[0])*(1-uv[1]), uv[0]*(1-uv[1]))
            loc = bary2(obj, particle)

            print(particle.fuv, loc)
            particle.location = loc
            particle.prev_location = loc
            slant = 0.5*(i-2)
            for k in range(dz):
                print(particle.hair_keys[k].co_local)
                x =  k*slant
                curvature = 3*(j-2)/dy
                if (curvature!=0):
                    r = math.pi/(curvature)
                    theta = k /r
                    y =  (1-math.cos(theta))*r
                    z = math.sin(theta)*r
                else:
                    y = 0
                    z=k
                particle.hair_keys[k].co_local = (x,y,z)
                print(debug_dump(k, particle))
          #      particle.hair_keys[k].co = particle.location + Vector( [x,y,z] )
          #      print(debug_dump(k, particle))
                #particle.hair_keys[k].co_local = (x,y,z)
                #print(debug_dump(k, particle))


def investigate1(obj):

    ps = obj.particle_systems[0]

    particle = ps.particles[-1]

    hk = particle.hair_keys[1]
    debug_dump(1, particle)

    hk.co_local = (0,0,0)
    print(debug_dump(1, particle))
    hk.co_local = (1,0,0)
    print(debug_dump(1, particle))
    hk.co_local = (0,1,0)
    print(debug_dump(1, particle))
    hk.co_local = (0,0,1)
    print(debug_dump(1, particle))

obj = bpy.data.objects['Plane']
print(obj)
comb2(obj)
#investigate1(obj)