"""Read a PDF's text layer and image positions with poppler. No guessing: coordinates in, text out."""
import os
import re
import subprocess
import tempfile
import xml.etree.ElementTree as ET


def _run(cmd):
    return subprocess.run(cmd, check=True, capture_output=True, text=True).stdout


def page_geometry(pdf):
    """[(width, height)] per page as displayed (rotation applied)."""
    n = int(re.search(r"^Pages:\s+(\d+)", _run(["pdfinfo", pdf]), re.M).group(1))
    out = _run(["pdfinfo", "-f", "1", "-l", str(n), pdf])
    sizes = {int(m[0]): (float(m[1]), float(m[2])) for m in re.findall(r"^Page\s+(\d+) size:\s+([\d.]+) x ([\d.]+)", out, re.M)}
    rots = {int(m[0]): int(m[1]) for m in re.findall(r"^Page\s+(\d+) rot:\s+(\d+)", out, re.M)}
    geo = []
    for p in range(1, n + 1):
        w, h = sizes[p]
        if rots.get(p, 0) in (90, 270):
            w, h = h, w
        geo.append((w, h))
    return geo


def halves(width, height):
    """A landscape page that holds two book pages is read as two units, left then right."""
    if width > height * 1.2:
        return [("L", 0, width / 2), ("R", width / 2, width / 2)]
    return [(None, 0, width)]


def chars_per_page(pdf):
    """Number of non-space characters in the text layer of each page."""
    n = len(page_geometry(pdf))
    out = []
    for p in range(1, n + 1):
        txt = _run(["pdftotext", "-f", str(p), "-l", str(p), pdf, "-"])
        out.append(len(re.sub(r"\s", "", txt)))
    return out


def units(pdf):
    """Reading units in order: [{'pdf_page', 'half', 'text'}]. Text keeps the layout (indentation, hyphens)."""
    result = []
    for p, (w, h) in enumerate(page_geometry(pdf), start=1):
        for half, x, width in halves(w, h):
            text = _run(["pdftotext", "-layout", "-f", str(p), "-l", str(p),
                         "-x", str(int(x)), "-y", "0", "-W", str(int(width)), "-H", str(int(h)), pdf, "-"])
            result.append({"pdf_page": p, "half": half, "text": text.replace("\f", "")})
    return result


def images(pdf):
    """Images with their page, half and pixel size: [{'pdf_page', 'half', 'width', 'height'}]."""
    geo = page_geometry(pdf)
    found = []
    with tempfile.TemporaryDirectory() as tmp:
        subprocess.run(["pdftohtml", "-xml", "-q", pdf, os.path.join(tmp, "o")], check=True, capture_output=True)
        root = ET.parse(os.path.join(tmp, "o.xml")).getroot()
        for page in root.iter("page"):
            p = int(page.get("number"))
            w, h = geo[p - 1]
            scale = float(page.get("width")) / w
            for img in page.iter("image"):
                cx = (float(img.get("left")) + float(img.get("width")) / 2) / scale
                half = None
                for name, x, width in halves(w, h):
                    if x <= cx < x + width:
                        half = name
                found.append({"pdf_page": p, "half": half,
                              "width": round(float(img.get("width")) / scale),
                              "height": round(float(img.get("height")) / scale)})
    return found