from __future__ import annotations

import os
import shutil
import subprocess
import tempfile
from pathlib import Path


class ExtractionError(RuntimeError):
    pass


def _run(cmd: list[str], *, cwd: str | None = None) -> subprocess.CompletedProcess[str]:
    return subprocess.run(cmd, cwd=cwd, check=True, capture_output=True, text=True)


def _looks_empty(text: str) -> bool:
    stripped = text.replace("\f", "").strip()
    return len(stripped) < 50


def extract_text(path: str) -> str:
    input_path = Path(path)
    if not input_path.exists():
        raise ExtractionError(f"Input not found: {input_path}")

    ext = input_path.suffix.lower()
    if ext in {".txt", ".md"}:
        return input_path.read_text(encoding="utf-8", errors="replace")

    if ext == ".pdf":
        return extract_text_from_pdf(str(input_path))

    raise ExtractionError(f"Unsupported file type: {ext}")


def extract_text_from_pdf(path: str) -> str:
    pdftotext = shutil.which("pdftotext")
    if not pdftotext:
        raise ExtractionError("Missing dependency: pdftotext (poppler-utils)")

    with tempfile.TemporaryDirectory(prefix="revoice-pdf-") as tmpdir:
        out_txt = os.path.join(tmpdir, "out.txt")
        _run([pdftotext, "-layout", path, out_txt])
        text = Path(out_txt).read_text(encoding="utf-8", errors="replace")

    if not _looks_empty(text):
        return text

    return ocr_pdf(path)


def ocr_pdf(path: str, *, dpi: int = 200, lang: str = "eng") -> str:
    pdftoppm = shutil.which("pdftoppm")
    tesseract = shutil.which("tesseract")
    if not pdftoppm:
        raise ExtractionError("Missing dependency: pdftoppm (poppler-utils)")
    if not tesseract:
        raise ExtractionError("Missing dependency: tesseract (tesseract-ocr)")

    with tempfile.TemporaryDirectory(prefix="revoice-ocr-") as tmpdir:
        prefix = os.path.join(tmpdir, "page")
        _run([pdftoppm, "-png", "-r", str(dpi), path, prefix])

        parts: list[str] = []
        for page_path in sorted(Path(tmpdir).glob("page-*.png")):
            header = f"===== {page_path.stem} ====="
            proc = subprocess.run(
                [tesseract, str(page_path), "stdout", "-l", lang, "--psm", "6"],
                check=True,
                capture_output=True,
                text=True,
            )
            parts.append(f"{header}\n{proc.stdout.strip()}\n")

    return "\n\n".join(parts).strip() + "\n"