import tempfile
import subprocess
import os.path
import string

SAFECHARS = string.ascii_letters + string.digits + " _-"


def extract_pages(source, bookmark, start=None, end=None, count=1):

    return extract_and_concat([(source, bookmark, start, end, count)])


def extract_and_concat(items):

    # create a temporary directory for our sections
    d = tempfile.TemporaryDirectory(prefix="polyphonic_")
    pdfmarks = os.path.join(d.name, "pdfmarks.txt")
    marks = open(pdfmarks, "w")

    sections = []
    current_page = 1

    for i, (source, bookmark, start, end, count) in enumerate(items):
        if count == 0:
            continue

        if not start:
            sections.append(source)

        else:
            if not end:
                end = start

            dest = os.path.join(d.name, f"section_{i}.pdf")

            cmd = [
                "gs",
                "-sDEVICE=pdfwrite",
                "-dBATCH",
                "-dNOPAUSE",
                f"-dFirstPage={start}",
                f"-dLastPage={end}",
                f"-sOutputFile={dest}",
                source,
            ]

            bookmark = "".join(filter(lambda c: c in SAFECHARS, bookmark))

            marks.write(f"[/Title ({bookmark}) /Page {current_page} /OUT pdfmark\n")

            p = subprocess.run(cmd, check=True, capture_output=True)
            pages = len(
                [
                    x
                    for x in p.stdout.splitlines()
                    if x.decode("utf8").startswith("Page ")
                ]
            )
            for j in range(count):
                sections.append(dest)
                current_page += pages

    marks.close()

    # concat the items
    output = tempfile.NamedTemporaryFile(prefix="polyphonic_", suffix=".pdf")

    cmd = ["gs", "-sDEVICE=pdfwrite", "-q", "-dBATCH", "-dNOPAUSE", "-sOutputFile=-"]
    cmd.extend(sections)
    cmd.append(pdfmarks)

    subprocess.run(cmd, stdout=output)

    output.seek(0)
    return output