import os.path
import numpy as np
from collections import OrderedDict


def contourlevelzero(md,mask,level):
    """CONTOURLEVELZERO - figure out the zero level (or offset thereof, 
    specified by the level value of a vectorial mask, and vectorialize it into 
    an exp or shp compatible structure.

    Usage:
        contours=contourlevelzero(md,mask,level)

        See also: PLOT_CONTOUR
    """

    # Process data 
    if md.mesh.dimension() == 3:
        x = md.mesh.x2d
        y = md.mesh.y2d
        z = md.mesh.z
        index = md.mesh.elements2d - 1
    else:
        x = md.mesh.x
        y = md.mesh.y
        index = md.mesh.elements - 1
        z = np.zeros((md.mesh.numberofvertices, 1))

    if len(mask) == 0:
        raise OSError("mask provided is empty")

    if md.mesh.dimension() == 3:
        if len(mask) != md.mesh.numberofvertices2d: 
            raise OSError("mask provided should be specified at the vertices of the mesh")
    else:
        if len(mask) != md.mesh.numberofvertices:
            raise OSError("mask provided should be specified at the vertices of the mesh")

    # Initialization of some variables
    numberofelements = np.size(index, 0)
    elementslist = np.c_[0:numberofelements]
    c = []
    h = []

    # Get unique edges in mesh
    # 1: list of edges
    edges = np.vstack((np.vstack((index[:, (0, 1)], index[:, (1, 2)])), index[:, (2, 0)]))
    # 2: find unique edges
    [edges, J] = np.unique(np.sort(edges, 1), axis=0, return_inverse=True)
    # 3: unique edge numbers
    vec = J
    # 4: unique edges numbers in each triangle (2 triangles sharing the same 
    # edge will have the same edge number)
    edges_tria = np.hstack((np.hstack((vec[elementslist], vec[elementslist + numberofelements])), vec[elementslist + 2 * numberofelements]))

    # Segments [nodes1 nodes2]
    Seg1 = index[:, (0, 1)]
    Seg2 = index[:, (1, 2)]
    Seg3 = index[:, (2, 0)]

    # Segment numbers [1;4;6;...]
    Seg1_num = edges_tria[:, 0]
    Seg2_num = edges_tria[:, 1]
    Seg3_num = edges_tria[:, 2]

    #value of data on each tips of the segments
    Data1 = mask[Seg1]
    Data2 = mask[Seg2]
    Data3 = mask[Seg3]

    # Get the ranges for each segment
    Range1 = np.sort(Data1, 1)
    Range2 = np.sort(Data2, 1)
    Range3 = np.sort(Data3, 1)

    # Find the segments that contain this value
    pos1 = (Range1[:, 0] < level) & (Range1[:, 1] >= level)
    pos2 = (Range2[:, 0] < level) & (Range2[:, 1] >= level)
    pos3 = (Range3[:, 0] < level) & (Range3[:, 1] >= level)

    # Get elements
    poselem12 = (pos1) & (pos2)
    poselem13 = (pos1) & (pos3)
    poselem23 = (pos2) & (pos3)
    poselem = np.where((poselem12) | (poselem13) | (poselem23))
    poselem = poselem[0]
    numelems = len(poselem)

    # If no element has been flagged, skip to the next level
    if numelems == 0:
        raise Exception('contourlevelzero warning message: no elements found with corresponding level value in mask')
        contours = []
        return contours

    # Go through the elements and build the coordinates for each segment (1 by element)
    x1 = np.zeros((numelems, 1))
    x2 = np.zeros((numelems, 1))
    y1 = np.zeros((numelems, 1))
    y2 = np.zeros((numelems, 1))
    z1 = np.zeros((numelems, 1))
    z2 = np.zeros((numelems, 1))

    edge_l = np.zeros((numelems, 2))

    for j in range(0, numelems):
        with np.errstate(divide='ignore', invalid='ignore'):
            weight1 = np.divide(level - Data1[poselem[j], 0],Data1[poselem[j], 1] - Data1[poselem[j], 0])
            weight2 = np.divide(level - Data2[poselem[j], 0],Data2[poselem[j], 1] - Data2[poselem[j], 0])
            weight3 = np.divide(level - Data3[poselem[j], 0],Data3[poselem[j], 1] - Data3[poselem[j], 0])

        if poselem12[poselem[j]] == True:
            x1[j] = x[Seg1[poselem[j], 0]] + weight1 * [x[Seg1[poselem[j], 1]] - x[Seg1[poselem[j], 0]]]
            x2[j] = x[Seg2[poselem[j], 0]] + weight2 * [x[Seg2[poselem[j], 1]] - x[Seg2[poselem[j], 0]]]
            y1[j] = y[Seg1[poselem[j], 0]] + weight1 * [y[Seg1[poselem[j], 1]] - y[Seg1[poselem[j], 0]]]
            y2[j] = y[Seg2[poselem[j], 0]] + weight2 * [y[Seg2[poselem[j], 1]] - y[Seg2[poselem[j], 0]]]
            z1[j] = z[Seg1[poselem[j], 0]] + weight1 * [z[Seg1[poselem[j], 1]] - z[Seg1[poselem[j], 0]]]
            z2[j] = z[Seg2[poselem[j], 0]] + weight2 * [z[Seg2[poselem[j], 1]] - z[Seg2[poselem[j], 0]]]

            edge_l[j, 0] = Seg1_num[poselem[j]]
            edge_l[j, 1] = Seg2_num[poselem[j]]
        elif poselem13[poselem[j]] == True:
            x1[j] = x[Seg1[poselem[j], 0]] + weight1 * [x[Seg1[poselem[j], 1]] - x[Seg1[poselem[j], 0]]]
            x2[j] = x[Seg3[poselem[j], 0]] + weight3 * [x[Seg3[poselem[j], 1]] - x[Seg3[poselem[j], 0]]]
            y1[j] = y[Seg1[poselem[j], 0]] + weight1 * [y[Seg1[poselem[j], 1]] - y[Seg1[poselem[j], 0]]]
            y2[j] = y[Seg3[poselem[j], 0]] + weight3 * [y[Seg3[poselem[j], 1]] - y[Seg3[poselem[j], 0]]]
            z1[j] = z[Seg1[poselem[j], 0]] + weight1 * [z[Seg1[poselem[j], 1]] - z[Seg1[poselem[j], 0]]]
            z2[j] = z[Seg3[poselem[j], 0]] + weight3 * [z[Seg3[poselem[j], 1]] - z[Seg3[poselem[j], 0]]]

            edge_l[j, 0] = Seg1_num[poselem[j]]
            edge_l[j, 1] = Seg3_num[poselem[j]]
        elif poselem23[poselem[j]] == True:
            x1[j] = x[Seg2[poselem[j], 0]] + weight2 * [x[Seg2[poselem[j], 1]] - x[Seg2[poselem[j], 0]]]
            x2[j] = x[Seg3[poselem[j], 0]] + weight3 * [x[Seg3[poselem[j], 1]] - x[Seg3[poselem[j], 0]]]
            y1[j] = y[Seg2[poselem[j], 0]] + weight2 * [y[Seg2[poselem[j], 1]] - y[Seg2[poselem[j], 0]]]
            y2[j] = y[Seg3[poselem[j], 0]] + weight3 * [y[Seg3[poselem[j], 1]] - y[Seg3[poselem[j], 0]]]
            z1[j] = z[Seg2[poselem[j], 0]] + weight2 * [z[Seg2[poselem[j], 1]] - z[Seg2[poselem[j], 0]]]
            z2[j] = z[Seg3[poselem[j], 0]] + weight3 * [z[Seg3[poselem[j], 1]] - z[Seg3[poselem[j], 0]]]

            edge_l[j, 0] = Seg2_num[poselem[j]]
            edge_l[j, 1] = Seg3_num[poselem[j]]
        # else:
        # Should never get here

    # Now that we have the segments, we must try to connect them...

    # Loop over the subcontours
    contours = []

    while len(edge_l) > 0:
        # Take the right edge of the second segment and connect it to the next segments if any
        e1 = edge_l[0, 0]
        e2 = edge_l[0, 1]
        xc = np.vstack((x1[0], x2[0]))
        yc = np.vstack((y1[0], y2[0]))
        zc = np.vstack((z1[0], z2[0]))
        # Erase the lines corresponding to this edge
        edge_l = np.delete(edge_l, 0, axis=0)
        x1 = np.delete(x1, 0, axis=0)
        x2 = np.delete(x2, 0, axis=0)
        y1 = np.delete(y1, 0, axis=0)
        y2 = np.delete(y2, 0, axis=0)
        z1 = np.delete(z1, 0, axis=0)
        z2 = np.delete(z2,0,axis=0)
        pos1 = np.where(edge_l == e1)
        
        while len(pos1[0]) > 0:
            if np.all(pos1[1] == 0):
                xc = np.vstack((x2[pos1[0]], xc))
                yc = np.vstack((y2[pos1[0]], yc))
                zc = np.vstack((z2[pos1[0]], zc))
                # Next edge:
                e1 = edge_l[pos1[0], 1]
            else:
                xc = np.vstack((x1[pos1[0]], xc))
                yc = np.vstack((y1[pos1[0]], yc))
                zc = np.vstack((z1[pos1[0]], zc))
                # Next edge:
                e1 = edge_l[pos1[0], 0]

            # Erase the lines of this
            edge_l = np.delete(edge_l, pos1[0], axis=0)
            x1 = np.delete(x1, pos1[0], axis=0)
            x2 = np.delete(x2, pos1[0], axis=0)
            y1 = np.delete(y1, pos1[0], axis=0)
            y2 = np.delete(y2, pos1[0], axis=0)
            z1 = np.delete(z1, pos1[0], axis=0)
            z2 = np.delete(z2, pos1[0], axis=0)
            # Next connection
            pos1 = np.where(edge_l == e1)

        # Same thing the other way (to the right)
        pos2 = np.where(edge_l == e2)

        while len(pos2[0]) > 0:
            if np.all(pos2[1] == 0):
                xc = np.vstack((xc, x2[pos2[0]]))
                yc = np.vstack((yc, y2[pos2[0]]))
                zc = np.vstack((zc, z2[pos2[0]]))
                # Next edge:
                e2 = edge_l[pos2[0], 1]
            else:
                xc = np.vstack((xc, x1[pos2[0]]))
                yc = np.vstack((yc, y1[pos2[0]]))
                zc = np.vstack((zc, z1[pos2[0]]))
                # Next edge:
                e2 = edge_l[pos2[0], 0]

            # Erase the lines of this
            edge_l = np.delete(edge_l, pos2[0], axis=0)
            x1 = np.delete(x1, pos2[0], axis=0)
            x2 = np.delete(x2, pos2[0], axis=0)
            y1 = np.delete(y1, pos2[0], axis=0)
            y2 = np.delete(y2, pos2[0], axis=0)
            z1 = np.delete(z1, pos2[0], axis=0)
            z2 = np.delete(z2, pos2[0], axis=0)
            # Next connection
            pos2 = np.where(edge_l == e2)

        # Save xc, yc contour:
        newcontour = OrderedDict()
        newcontour['nods'] = np.size(xc)
        newcontour['density'] = 1
        newcontour['closed'] = 0
        newcontour['x'] = np.ma.filled(xc.astype(float), np.nan)
        newcontour['y'] = np.ma.filled(yc.astype(float), np.nan)
        newcontour['z'] = np.ma.filled(zc.astype(float), np.nan)
        newcontour['name'] = ''
        contours.append(newcontour)

    return contours