import subprocess
from pathlib import Path

from pikepdf import (
    Page,
    Operator,
    Pdf,
    Stream,
    parse_content_stream,
    unparse_content_stream,
)

# input file
infile: Path = Path.cwd().joinpath("rtl8196e-vex-cg-datasheet-1.1.pdf")
# object matcher
wmark_colours = (0.8, 0.8, 0.8)

# intermediary qdf file
qdf_file: Path = infile.with_suffix(".qdf")
# output file
outfile: Path = infile.with_stem(f"{infile.stem}.clean")

# function to strip watermark text from a page
def strip_watermark_text(pdf: Pdf, page: Page, watermark_colors: tuple):
    stream = []
    in_text_obj = False
    color_values = (0.0, 0.0, 0.0)
    text_objects = []

    for operands, operator in parse_content_stream(page, ""):
        if not in_text_obj:
            if operator == Operator("BT"):
                in_text_obj = True
                color_values = (0.0, 0.0, 0.0)
                text_objects.append((operands, operator))
            else:
                stream.append((operands, operator))
        else:
            if operator == Operator("rg"):
                color_values = (float(operands[0]), float(operands[1]), float(operands[2]))
            text_objects.append((operands, operator))
            if operator == Operator("ET"):
                in_text_obj = False
                if color_values != watermark_colors:
                    stream.extend(text_objects)
                text_objects.clear()

    content_stream = unparse_content_stream(stream)
    page.Contents = Stream(pdf, content_stream)


if __name__ == "__main__":
    # Convert to QDF
    # qpdf --qdf --stream-data=uncompress infile outfile
    print("Converting PDF to QDF...")
    result = subprocess.call(["qpdf", "--qdf", "--stream-data=uncompress", infile, qdf_file])
    if result != 0:
        raise RuntimeError("qpdf failed parsing the PDF file to QDF")

    # open the QDF as a pikepdf object
    print("Opening QDF file as pikepdf object...")
    document: Pdf = Pdf.open(qdf_file)

    print("Processing pages...")
    for page in document.pages:
        print(f"{page.index}", end=" ")
        strip_watermark_text(document, page, wmark_colours)

    print(f"Saving to {outfile} ...")
    document.save(outfile)

    print(f"Removing {qdf_file} ...")
    qdf_file.unlink()

    print("Done! Hopefully...")