import os
import subprocess

import jinja2

# =============================================================================
def generate_outfile(
        templatesdir,
        templatename,
        context,
        outfilename,
        log = None,
        ):

    # Template rendering
    # -------------------------------------------------------------------------
    log.info("Generating SVG using '{}' template".format(templatename))

    jj2_env = jinja2.Environment(
            loader = jinja2.FileSystemLoader( templatesdir )
            )

    try:
        jj2_tpl = jj2_env.get_template(
                os.path.join(
                    templatename,
                    "template.svg.j2",
                    )
                )
    except:
        log.error("Could not find template '{}'".format(templatename))
        return None

    extension = outfilename.split(".")[-1]

    # To SVG
    # -------------------------------------------------------------------------
    if extension == "svg":
        jj2_tpl.stream(context).dump( outfilename )
        return outfilename

    # To PNG with inkscape
    # -------------------------------------------------------------------------
    if extension == "png":

        try:
            log.info("Exporting to {} using inkscape".format(extension))
            import subprocess

            jj2_tpl.stream(context).dump( "tmp.svg" )

            inkscape_process = subprocess.Popen(
                    [
                        "inkscape",
                        "tmp.svg",
                        "--export-filename",
                        outfilename,
                        ],
                    stdout = subprocess.PIPE,
                    stderr = subprocess.STDOUT,
                    universal_newlines = True,
                    )

            for line_out in iter(inkscape_process.stdout.readline, ""):
                log.debug(line_out)

            inkscape_process.stdout.close()

            rv = inkscape_process.wait()

            if rv != 0:
                raise Exception(
                        "Bad inkscape return code '{}'" \
                                .format(inkscape_process.returncode)
                                )

            return outfilename

        except Exception as e:
            log.warning("Failed to export with inkscape")
            try:
                os.unlink("tmp.svg")
            except:
                pass
            log.debug(e)

    # To png, pdf or ps with cairosvg
    # -------------------------------------------------------------------------
    if extension in [ "png", "pdf", "ps" ]:

        log.info("Exporting to {} using cairosvg".format(extension))

        try:
            import cairosvg
        except ImportError as e:
            log.error(
                    "Failed to export to '{}' with cairosvg" \
                            .format(
                                outfilename,
                                )
                            )
            log.debug(e)

        svg_str = jj2_tpl.render(context)

        if extension == "png":
            conversion_fun = cairosvg.svg2png
        elif extension == "pdf":
            conversion_fun = cairosvg.svg2pdf
        elif extension == "ps":
            conversion_fun = cairosvg.svg2ps

        conversion_fun(
            bytestring = svg_str,
            write_to = outfilename,
            )

        return outfilename

    # To unsupported format
    # -------------------------------------------------------------------------
    log.error(
            "Can't export to '{}' : unsupported format '{}'" \
                    .format(
                        outfilename,
                        extension,
                        )
                    )
    return None