#! /usr/bin/python3
# Last edited on 2026-03-25 04:27:28 by stolfi

import os, sys, re
from sys import stderr as err
import numpy as nu
import cairo
from process_funcs import bash
from math import sqrt, log, exp, nan, inf, pi, floor, ceil, isfinite, isnan

def main(set_name):

  def ok(p): 
    return isfinite(p[0]) and p[0] >= 0 and isfinite(p[1]) and p[1] >= 0
    # ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
    
  # Read point files:
  pts_file_a = f"keyframes/{set_name}-0.txt"
  pts_file_b = f"keyframes/{set_name}-1.txt"
  pts_file_c = f"keyframes/{set_name}-2.txt"
  pts_a = nu.loadtxt(pts_file_a)
  pts_b = nu.loadtxt(pts_file_b)
  pts_c = nu.loadtxt(pts_file_c)
  err.write(f"{nu.shape(pts_a) = }\n")
  pts = nu.zeros(nu.shape(pts_a))
  pts_nan = nu.full((2,), nan)
  err.write(f"{nu.shape(pts_nan) = }\n")
  np = nu.size(pts_a, 0)
  err.write(f"{np = }\n")
  # Generate 30 frames for the a -> b transition
  nf = 30
  frames = []
  for kf in range(nf):
    t = kf / (nf-1)
    # Interpolating quadratic basis:
    Pa = 2*(t - 0.5)*(t - 1.0)
    Pb = 4*t*(1-t)
    Pc = 2*t*(t - 0.5)

    # Image size
    width, height = 300, 300

    # Create surface, paint all white:
    surface = cairo.ImageSurface(cairo.FORMAT_RGB24, width, height)
    ctx = cairo.Context(surface)
    ctx.set_source_rgb(1, 1, 1)
    ctx.paint()

    # Set stroke properties
    ctx.set_source_rgb(1, 0, 0)        # red
    ctx.set_line_width(30.0)
    ctx.set_line_cap(cairo.LINE_CAP_ROUND)
    ctx.set_line_join(cairo.LINE_JOIN_ROUND)

    in_path = False 
    for ip in range(np+1):
      # Interpolate point
      pa = pts_a[ip,:] if ip < np else pts_nan
      pb = pts_b[ip,:] if ip < np else pts_nan
      pc = pts_c[ip,:] if ip < np else pts_nan
      if ip < np and ok(pa) and ok(pb) and ok(pc):
        p = Pa*pa + Pb*pb + Pc*pc
        if not in_path:
          ctx.move_to(p[0], p[1])
        else:
          ctx.line_to(p[0], p[1])
        in_path = True
      else:
        ctx.stroke()
        in_path = False

    # Draw the polygonal:
    out_file = f"frames/{set_name}-{kf:03d}.png"
    surface.write_to_png(out_file)
  return
  # ----------------------------------------------------------------------

main(sys.argv[1])