import os
import shutil
from tempfile import mkdtemp

from pdfminer.high_level import extract_text

from textract.exceptions import ShellError, UnknownMethod

from .image import Parser as TesseractParser
from .utils import ShellParser


class Parser(ShellParser):
    """Extract text from pdf files using either the ``pdftotext`` method
    (default) or the ``pdfminer`` method.
    """

    def extract(self, filename, method="", **kwargs):
        if method in {"", "pdftotext"}:
            try:
                return self.extract_pdftotext(filename, **kwargs)
            except ShellError as ex:
                # If pdftotext isn't installed and the pdftotext method
                # wasn't specified, then gracefully fallback to using
                # pdfminer instead.
                if method == "" and ex.is_not_installed():
                    return self.extract_pdfminer(filename, **kwargs)
                raise

        elif method == "pdfminer":
            return self.extract_pdfminer(filename, **kwargs)
        elif method == "tesseract":
            return self.extract_tesseract(filename, **kwargs)
        else:
            raise UnknownMethod(method)

    def extract_pdftotext(self, filename, **kwargs):
        """Extract text from pdfs using the pdftotext command line utility."""
        if "layout" in kwargs:
            args = ["pdftotext", "-layout", filename, "-"]
        else:
            args = ["pdftotext", filename, "-"]
        stdout, _ = self.run(args)
        return stdout

    def extract_pdfminer(self, filename, **kwargs):
        """Extract text from pdfs using pdfminer."""
        return extract_text(filename).encode("utf-8")

    def extract_tesseract(self, filename, **kwargs):
        """Extract text from pdfs using tesseract (per-page OCR)."""
        temp_dir = mkdtemp()
        base = os.path.join(temp_dir, "conv")
        contents = []
        try:
            stdout, _ = self.run(["pdftoppm", filename, base])

            for page in sorted(os.listdir(temp_dir)):
                page_path = os.path.join(temp_dir, page)
                page_content = TesseractParser().extract(page_path, **kwargs)
                contents.append(page_content)
            return b"".join(contents)
        finally:
            shutil.rmtree(temp_dir)