#! /usr/bin/env python

# file lyxpreview2bitmap.py
# This file is part of LyX, the document processor.
# Licence details can be found in the file COPYING.

# author Angus Leeming
# with much advice from members of the preview-latex project:
# David Kastrup, dak@gnu.org and
# Jan-Åke Larsson, jalar@mai.liu.se.

# Full author contact details are available in file CREDITS

# This script takes a LaTeX file and generates a collection of
# png or ppm image files, one per previewed snippet.

# Pre-requisites:
# * A latex executable;
# * preview.sty;
# * dvipng;
# * pngtoppm (if outputing ppm format images).

# preview.sty and dvipng are part of the preview-latex project
# http://preview-latex.sourceforge.net/

# preview.sty can alternatively be obtained from
# CTAN/support/preview-latex/

# Example usage:
# lyxpreview2bitmap.py png 0lyxpreview.tex 128 000000 faf0e6

# This script takes five arguments:
# FORMAT:   either 'png' or 'ppm'. The desired output format.
# TEXFILE:  the name of the .tex file to be converted.
# DPI:      a scale factor, passed to dvipng.
# FG_COLOR: the foreground color as a hexadecimal string, eg '000000'.
# BG_COLOR: the background color as a hexadecimal string, eg 'faf0e6'.

# Decomposing TEXFILE's name as DIR/BASE.tex, this script will,
# if executed successfully, leave in DIR:
# * a (possibly large) number of image files with names
#   like BASE[0-9]+.png
# * a file BASE.metrics, containing info needed by LyX to position
#   the images correctly on the screen.

import glob, os, re, string, sys
from legacy_lyxpreview2ppm import legacy_conversion


# Pre-compiled regular expressions.
hexcolor_re = re.compile("^[0-9a-fA-F]{6}$")
latex_file_re = re.compile("\.tex$")


def usage(prog_name):
    return "Usage: %s <latex file> <dpi> <fg color> <bg color>\n"\
           "\twhere the colors are hexadecimal strings, eg 'faf0e6'"\
           % prog_name


def error(message):
    sys.stderr.write(message + '\n')
    sys.exit(1)


def find_exe(candidates, path):
    for prog in candidates:
        for directory in path:
            full_path = os.path.join(directory, prog)
            if os.access(full_path, os.X_OK):
                return full_path

    return None


def find_exe_or_terminate(candidates, path):
    exe = find_exe(candidates, path)
    if exe == None:
        error("Unable to find executable from '%s'" % string.join(candidates))

    return exe


def run_command(cmd):
    handle = os.popen(cmd, 'r')
    cmd_stdout = handle.read()
    cmd_status = handle.close()

    return cmd_status, cmd_stdout


def make_texcolor(hexcolor):
    # Test that the input string contains 6 hexadecimal chars.
    if not hexcolor_re.match(hexcolor):
        error("Cannot convert color '%s'" % hexcolor)

    red   = float(string.atoi(hexcolor[0:2], 16)) / 255.0
    green = float(string.atoi(hexcolor[2:4], 16)) / 255.0
    blue  = float(string.atoi(hexcolor[4:6], 16)) / 255.0

    return "rgb %f %f %f" % (red, green, blue)


def extract_metrics_info(dvipng_stdout, metrics_file):
    metrics = open(metrics_file, 'w')
    metrics_re = re.compile("\[([0-9]+) depth=(-?[0-9]+) height=(-?[0-9]+)")

    success = 0
    pos = 0
    while 1:
        match = metrics_re.search(dvipng_stdout, pos)
        if match == None:
            break
        success = 1

        # Calculate the 'ascent fraction'.
        descent = string.atof(match.group(2))
        ascent  = string.atof(match.group(3))
        frac = 0.5
        if abs(ascent + descent) > 0.1:
            frac = ascent / (ascent + descent)

        metrics.write("Snippet %s %f\n" % (match.group(1), frac))
        pos = match.end(3) + 2

    return success


def convert_to_ppm_format(pngtopnm, basename):
    png_file_re = re.compile("\.png$")

    for png_file in glob.glob("%s*.png" % basename):
        ppm_file = png_file_re.sub(".ppm", png_file)

        p2p_cmd = "%s %s" % (pngtopnm, png_file)
        p2p_status, p2p_stdout = run_command(p2p_cmd)
        if p2p_status != None:
            error("Unable to convert %s to ppm format" % png_file)

        ppm = open(ppm_file, 'w')
        ppm.write(p2p_stdout)
        os.remove(png_file)


def main(argv):
    # Parse and manipulate the command line arguments.
    if len(argv) != 6:
        error(usage(argv[0]))

    output_format = string.lower(argv[1])

    dir, latex_file = os.path.split(argv[2])
    if len(dir) != 0:
        os.chdir(dir)

    dpi = string.atoi(argv[3])
    fg_color = make_texcolor(argv[4])
    bg_color = make_texcolor(argv[5])

    # External programs used by the script.
    path = string.split(os.getenv("PATH"), os.pathsep)
    latex = find_exe_or_terminate(["pplatex", "latex2e", "latex"], path)

    # This can go once dvipng becomes widespread.
    dvipng = find_exe(["dvipng"], path)
    if dvipng == None:
        if output_format == "ppm":
            return legacy_conversion(argv)
        else:
            error("The old 'dvi->ps->ppm' conversion requires "
                  "ppm as the output format")

    pngtopnm = ""
    if output_format == "ppm":
        pngtopnm = find_exe_or_terminate(["pngtopnm"], path)

    # Compile the latex file.
    latex_call = "%s %s" % (latex, latex_file)

    latex_status, latex_stdout = run_command(latex_call)
    if latex_status != None:
        error("%s failed to compile %s" \
              % (os.path.basename(latex), latex_file))

    # Run the dvi file through dvipng.
    dvi_file = latex_file_re.sub(".dvi", latex_file)
    dvipng_call = "%s -Ttight -depth -height -D %d -fg '%s' -bg '%s' %s" \
                  % (dvipng, dpi, fg_color, bg_color, dvi_file)

    dvipng_status, dvipng_stdout = run_command(dvipng_call)
    if dvipng_status != None:
        error("%s failed to generate images from %s" \
              % (os.path.basename(dvipng), dvi_file))

    # Extract metrics info from dvipng_stdout.
    metrics_file = latex_file_re.sub(".metrics", latex_file)
    if not extract_metrics_info(dvipng_stdout, metrics_file):
        error("Failed to extract metrics info from dvipng")

    # Convert images to ppm format if necessary.
    if output_format == "ppm":
        convert_to_ppm_format(pngtopnm, latex_file_re.sub("", latex_file))

    return 0

if __name__ == "__main__":
    main(sys.argv)