import os
import subprocess
import tempfile

import jinja2

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

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

    log.debug(
            "Initializing jinja2 with template dir '{}'" \
                    .format(templatesdir)
                    )
    jj2_env = jinja2.Environment(
            loader = jinja2.FileSystemLoader(
                str(templatesdir),
                )
            )

    try:
        jj2_tpl = jj2_env.get_template(
                # Jinja specific path format
                "{}/template.svg.j2".format(templatename),
                )
    except Exception as e:
        log.error("Could not find template '{}'".format(templatename))
        log.debug(e, exc_info=1)
        return None

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

    # To PNG with inkscape
    # -------------------------------------------------------------------------
    if outfilename.suffix == ".png":

        cachedir.mkdir(parents=True, exist_ok=True)

        with tempfile.NamedTemporaryFile(
                suffix="svg",
                dir = str(cachedir),
                ) as tmpsvg:
            try:
                log.info(
                        "Exporting to {} using inkscape" \
                                .format(outfilename.suffix),
                                )
                import subprocess

                jj2_tpl.stream(context).dump( tmpsvg )

                inkscape_process = subprocess.Popen(
                        [
                            "inkscape",
                            tmpsvg.name,
                            "--export-filename",
                            str(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")
                log.debug(e)

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

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

        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 outfilename.suffix == ".png":
            conversion_fun = cairosvg.svg2png
        elif outfilename.suffix == ".pdf":
            conversion_fun = cairosvg.svg2pdf
        elif outfilename.suffix == ".ps":
            conversion_fun = cairosvg.svg2ps

        conversion_fun(
            bytestring = svg_str,
            write_to = str(outfilename),
            )

        return outfilename

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