"""Conversation export helpers kept separate from Flask request handling."""

import os
import re
from typing import Iterable, Mapping


def _unicode_font(base_dir: str) -> str:
    candidates = [
        os.path.join(base_dir, "fonts", "NotoSans-Regular.ttf"),
        "/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf",
        r"C:\Windows\Fonts\arial.ttf",
    ]
    return next((candidate for candidate in candidates if os.path.exists(candidate)), "")


def _core_font_text(value) -> str:
    text = str(value or "")
    replacements = {
        "→": " -> ", "⇒": " => ", "—": " - ", "–": " - ",
        "‘": "'", "’": "'", "“": '"', "”": '"', "…": "...",
        "•": "-", "✓": "[done]", "✗": "[failed]",
    }
    for source, replacement in replacements.items():
        text = text.replace(source, replacement)
    return text.encode("latin-1", "replace").decode("latin-1")


def _readable_export_text(value) -> str:
    text = str(value or "")
    text = re.sub(r"^#{1,6}\s+", "", text, flags=re.MULTILINE)
    text = text.replace("**", "").replace("__", "")
    text = re.sub(r"^- \[ \]\s+", "[ ] ", text, flags=re.MULTILINE)
    text = re.sub(r"^- \[[xX]\]\s+", "[done] ", text, flags=re.MULTILINE)
    return text


def create_conversation_pdf(messages: Iterable[Mapping[str, str]], output_path: str, base_dir: str) -> str:
    """Create a paginated export without silently truncating normal conversation turns."""
    from fpdf import FPDF

    class ConversationPDF(FPDF):
        def header(self):
            if self.page_no() <= 1:
                return
            self.set_font("Helvetica", "", 8)
            self.set_text_color(90, 100, 115)
            self.cell(0, 6, "Invicta AI Conversation Export", align="R")
            self.ln(10)
            self.set_text_color(0, 0, 0)

        def footer(self):
            self.set_y(-12)
            self.set_font("Helvetica", "", 8)
            self.set_text_color(110, 120, 132)
            self.cell(0, 6, f"Page {self.page_no()}/{{nb}}", align="C")

    pdf = ConversationPDF()
    pdf.alias_nb_pages()
    pdf.set_title("Invicta AI Conversation Export")
    pdf.set_author("InvictaTill AI")
    pdf.set_auto_page_break(auto=True, margin=15)
    pdf.add_page()
    font_path = _unicode_font(base_dir)
    if font_path:
        pdf.add_font("InvictaUnicode", "", font_path)
        pdf.set_font("InvictaUnicode", "", 16)
    else:
        pdf.set_font("Helvetica", "B", 16)
    pdf.cell(0, 10, "Invicta AI Conversation Export", new_x="LMARGIN", new_y="NEXT", align="C")
    pdf.ln(5)

    for message in messages:
        role = str(message.get("role", "user")).upper()
        content = _readable_export_text(str(message.get("content", ""))[:20_000])
        if not font_path:
            role = _core_font_text(role)
            content = _core_font_text(content)
        pdf.set_font("InvictaUnicode" if font_path else "Helvetica", "" if font_path else "B", 11)
        pdf.multi_cell(0, 6, f"[{role}]", new_x="LMARGIN", new_y="NEXT")
        pdf.set_font("InvictaUnicode" if font_path else "Helvetica", "", 10)
        pdf.multi_cell(0, 5.5, content, new_x="LMARGIN", new_y="NEXT")
        pdf.ln(2)

    pdf.output(output_path)
    return output_path