# -*- coding: utf-8 -*-
# Copyright: Damien Elmes <anki@ichi2.net>
# License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html

import re, os, shutil, cgi
from anki.utils import checksum, call, namedtmp, tmpdir, isMac, stripHTML
from anki.hooks import addHook
from anki.lang import _

# extension we output
outputFileExt = "svg"
# extensions of existing images we look for
supportedExts = ["svg", "png"]

# if you modify these in an add-on, you must make sure to take tmp.tex as the
# input, and change outputFileExt to the output file extension
latexCmds = [
    ["latex", "-interaction=nonstopmode", "tmp.tex"],
    ["dvisvgm", "--no-fonts", "-Z", "2", "tmp.dvi", "-o", "tmp.%s" % outputFileExt]
]

build = True # if off, use existing media but don't create new
regexps = {
    "standard": re.compile(r"\[latex\](.+?)\[/latex\]", re.DOTALL | re.IGNORECASE),
    "expression": re.compile(r"\[\$\](.+?)\[/\$\]", re.DOTALL | re.IGNORECASE),
    "math": re.compile(r"\[\$\$\](.+?)\[/\$\$\]", re.DOTALL | re.IGNORECASE),
    }

# add standard tex install location to osx
if isMac:
    os.environ['PATH'] += ":/usr/texbin:/Library/TeX/texbin"

def stripLatex(text):
    for match in regexps['standard'].finditer(text):
        text = text.replace(match.group(), "")
    for match in regexps['expression'].finditer(text):
        text = text.replace(match.group(), "")
    for match in regexps['math'].finditer(text):
        text = text.replace(match.group(), "")
    return text

def mungeQA(html, type, fields, model, data, col):
    "Convert TEXT with embedded latex tags to image links."
    for match in regexps['standard'].finditer(html):
        html = html.replace(match.group(), _imgLink(col, match.group(1), model))
    for match in regexps['expression'].finditer(html):
        html = html.replace(match.group(), _imgLink(
            col, "$" + match.group(1) + "$", model))
    for match in regexps['math'].finditer(html):
        html = html.replace(match.group(), _imgLink(
            col,
            "\\begin{displaymath}" + match.group(1) + "\\end{displaymath}", model))
    return html

def _imgLink(col, latex, model):
    "Return an img link for LATEX, creating if necesssary."
    txt = _latexFromHtml(col, latex)

    # is there an existing file?
    fnamePrefix = "latex-%s." % checksum(txt.encode("utf8"))
    found = False
    for ext in supportedExts:
        fname = fnamePrefix + ext
        if os.path.exists(fname):
            found = True
            break
    if not found:
        fname = fnamePrefix + outputFileExt
    link = '<img class=latex src="%s">' % fname
    if found:
        return link

    # building disabled?
    if not build:
        return "[latex]%s[/latex]" % latex

    err = _buildImg(col, txt, fname, model)
    if err:
        return err
    else:
        return link

def _latexFromHtml(col, latex):
    "Convert entities and fix newlines."
    latex = re.sub("<br( /)?>|<div>", "\n", latex)
    latex = stripHTML(latex)
    return latex

def _buildImg(col, latex, fname, model):
    # add header/footer
    latex = (model["latexPre"] + "\n" +
             latex + "\n" +
             model["latexPost"])
    # it's only really secure if run in a jail, but these are the most common
    tmplatex = latex.replace("\\includegraphics", "")
    for bad in ("\\write18", "\\readline", "\\input", "\\include",
                "\\catcode", "\\openout", "\\write", "\\loop",
                "\\def", "\\shipout"):
        # don't mind if the sequence is only part of a command
        bad_re = "\\" + bad + "[^a-zA-Z]"
        if re.search(bad_re, tmplatex):
            return _("""\
For security reasons, '%s' is not allowed on cards. You can still use \
it by placing the command in a different package, and importing that \
package in the LaTeX header instead.""") % bad
    # write into a temp file
    log = open(namedtmp("latex_log.txt"), "w")
    texpath = namedtmp("tmp.tex")
    texfile = open(texpath, "w")
    texfile.write(latex)
    texfile.close()
    mdir = col.media.dir()
    oldcwd = os.getcwd()
    png = namedtmp("tmp.%s" % outputFileExt)
    try:
        # generate png
        os.chdir(tmpdir())
        for latexCmd in latexCmds:
            if call(latexCmd, stdout=log, stderr=log):
                return _errMsg(latexCmd[0], texpath)
        # add to media
        shutil.copyfile(png, os.path.join(mdir, fname))
        return
    finally:
        os.chdir(oldcwd)

def _errMsg(type, texpath):
    msg = (_("Error executing %s.") % type) + "<br>"
    msg += (_("Generated file: %s") % texpath) + "<br>"
    try:
        log = open(namedtmp("latex_log.txt", rm=False)).read()
        if not log:
            raise Exception()
        msg += "<small><pre>" + cgi.escape(log) + "</pre></small>"
    except:
        msg += _("Have you installed latex and dvipng?")
        pass
    return msg

# setup q/a filter
addHook("mungeQA", mungeQA)