from __future__ import annotations

import logging
from reportlab.lib.pagesizes import A4
from reportlab.pdfgen import canvas

logger = logging.getLogger(__name__)

_MARGIN = 72
_FONT_SIZE = 10
_LINE_HEIGHT = 14


def generate_text_pdf(text: str, output_path: str) -> None:
    """Generate a single-page PDF containing the given plain text.

    Text is rendered with automatic wrapping and page breaks for long chunks.
    Raises on I/O or reportlab errors — caller should handle gracefully.
    """
    c = canvas.Canvas(output_path, pagesize=A4)
    width, height = A4
    usable_width = width - 2 * _MARGIN
    y = height - _MARGIN

    for paragraph in text.split("\n"):
        if not paragraph.strip():
            y -= _LINE_HEIGHT
            if y < _MARGIN:
                c.showPage()
                y = height - _MARGIN
            continue

        lines = _wrap_text(paragraph, usable_width, c)
        for line in lines:
            if y < _MARGIN:
                c.showPage()
                y = height - _MARGIN
            c.drawString(_MARGIN, y, line)
            y -= _LINE_HEIGHT

    c.save()


def _wrap_text(text: str, max_width: float, canvas_obj: canvas.Canvas) -> list[str]:
    """Wrap text to fit within max_width using the canvas's stringWidth."""
    words = text.split()
    lines: list[str] = []
    current_line = ""

    for word in words:
        test_line = f"{current_line} {word}".strip() if current_line else word
        if canvas_obj.stringWidth(test_line, "Helvetica", _FONT_SIZE) <= max_width:
            current_line = test_line
        else:
            if current_line:
                lines.append(current_line)
            current_line = word

    if current_line:
        lines.append(current_line)

    return lines