"""Turns a Markdown summary into the summary report.

The summary is written by hand, beside the scan's artifacts, and reads as a document of its own: a
title, a few lines saying what it covers, then one section per source. This module sets it in the
dress of the full report -- the same cover, running header and footers, table of contents, headings
and tables -- so the two sit together as one series.

No design of its own. The Markdown is rendered to HTML whose elements are the ones ``report.css``
already styles, by moving them onto the full report's heading levels and classes:

- The first level-one heading is the title. Written as ``<title>: <subject>``, the subject is the
  project, unless one is given.
- What comes before the first section is the introduction, and goes on the cover.
- Every further level-one or level-two heading is a section: it starts a new page, as the full
  report's sections do, is listed in the table of contents and keeps the anchor GitHub would give it, so the links a
  summary makes to its own sections go on working in the PDF.
- A paragraph that is nothing but bold text is the subheading it is being used as.
- Tables are drawn as the full report's grids. A number in a severity or CVSS column carries its
  severity colour, and a row that opens with a bold ``Total`` is set as a total.
"""

from __future__ import annotations

import re
from datetime import UTC, datetime
from typing import TYPE_CHECKING, Any

from markdown_it import MarkdownIt
from markupsafe import Markup

from .context import UNKNOWN, _fact, _stated
from .layout import render_pdf
from .severity import _score_band

if TYPE_CHECKING:
    from uuid import UUID

    from markdown_it.token import Token

TEMPLATE_NAME = "summary.html.j2"

# What the document calls itself when the Markdown does not say.
TITLE = "Security Scan Summary"

# The shape the summary template expects.
CONTEXT = {
    "cover": "subject, footer, footer_date, logo, title, identity[], intro?",
    "contents": "[{id, title}]",
    "body": "the rendered sections",
}

# What the file is called: after the scan where there is one, else after the project.
NAME = "summary_{name}.pdf"

# A column whose numbers are CVSS scores, to be coloured by the band each falls in.
_SCORED_COLUMN = re.compile(r"severity|cvss|score", re.IGNORECASE)

_SCORE = re.compile(r"\d+(?:\.\d+)?")

# Where Markdown's heading levels land on the full report's: a section is its ``h1``, and what is
# under it one and two steps down.
_LEVELS = {"h1": "h1", "h2": "h1", "h3": "h2", "h4": "h3", "h5": "h3", "h6": "h3"}


def render_summary(
    markdown: str,
    *,
    scan_id: UUID | None = None,
    project: str | None = None,
    manufacturer: str | None = None,
) -> tuple[str, bytes]:
    """Render a Markdown summary as a PDF.

    Args:
        markdown: The summary.
        scan_id: The scan it is about, if it is to say so.
        project: The project name; overrides the subject of the title.
        manufacturer: Who makes the scanned product.

    Returns:
        The file name the summary should be saved under, and its bytes.
    """
    context = build_summary_context(markdown, scan_id=scan_id, project=project, manufacturer=manufacturer)
    name = str(scan_id) if scan_id else _slug(context["cover"]["subject"]) or "report"

    return NAME.format(name=name), render_pdf(context, TEMPLATE_NAME, context["cover"]["title"])


def build_summary_context(
    markdown: str,
    *,
    scan_id: UUID | None = None,
    project: str | None = None,
    manufacturer: str | None = None,
) -> dict[str, Any]:
    """Map a Markdown summary onto the page.

    Args:
        markdown: The summary.
        scan_id: The scan it is about, if it is to say so.
        project: The project name; overrides the subject of the title.
        manufacturer: Who makes the scanned product.

    Returns:
        The page-ready context; see :data:`CONTEXT`.
    """
    parser = MarkdownIt("commonmark").enable(["table", "strikethrough"])
    tokens = parser.parse(markdown)

    heading = _title(tokens)
    title, _, subject = heading.partition(":") if heading else (TITLE, "", "")
    project = project or subject.strip() or None

    contents = _sections(tokens, parser)
    _subheadings(tokens)
    _tables(tokens)

    start = next((index for index, token in enumerate(tokens) if token.meta.get("section")), len(tokens))
    intro, body = tokens[:start], tokens[start:]

    render = parser.renderer.render
    identity = [
        _fact("Manufacturer", manufacturer),
        _fact("Project", project),
        _fact("Report Created", datetime.now(UTC).strftime("%A, %B %d, %Y")),
    ]
    if scan_id:
        identity.append(_fact("Scan Identifier", scan_id, kind="mono"))

    return {
        "cover": {
            "subject": _stated(project),
            "footer": f"Scan: {scan_id}" if scan_id else _stated(project),
            "footer_date": datetime.now(UTC).strftime("%d %B %Y"),
            "logo": "cc_logo.png",
            "title": title.strip(),
            "identity": identity,
            "intro": Markup(render(intro, parser.options, {})) if intro else None,  # noqa: S704
        },
        "contents": contents,
        "body": Markup(render(body, parser.options, {})),  # noqa: S704
    }


def _title(tokens: list[Token]) -> str | None:
    """Take the first level-one heading out of the document, and say what it read."""
    for index, token in enumerate(tokens):
        if token.type == "heading_open" and token.tag == "h1":
            text = tokens[index + 1].content
            del tokens[index : index + 3]

            return text

    return None


def _sections(tokens: list[Token], parser: MarkdownIt) -> list[dict[str, Any]]:
    """Move every heading onto the full report's levels, and list the sections for the contents."""
    contents: list[dict[str, Any]] = []
    taken: set[str] = set()

    for index, token in enumerate(tokens):
        if token.type not in ("heading_open", "heading_close"):
            continue

        section = token.tag in ("h1", "h2")
        token.tag = _LEVELS[token.tag]
        if token.type == "heading_close" or not section:
            continue

        inline = tokens[index + 1]
        anchor = _unique(_github_anchor(inline.content), taken)
        token.attrSet("id", anchor)
        token.meta["section"] = True
        # As in the full report, every section opens a page of its own.
        token.attrSet("style", "break-before: page")
        title = Markup(parser.renderer.render(inline.children or [], parser.options, {}))  # noqa: S704
        contents.append({"id": anchor, "title": title})

    return contents


def _subheadings(tokens: list[Token]) -> None:
    """Set a paragraph that is nothing but bold text as the subheading it stands in for."""
    for index, token in enumerate(tokens):
        if token.type != "paragraph_open" or token.hidden:
            continue

        children = tokens[index + 1].children or []
        kinds = [child.type for child in children]
        if kinds == ["strong_open", "text", "strong_close"]:
            token.tag = tokens[index + 2].tag = "h2"
            tokens[index + 1].children = [children[1]]


def _tables(tokens: list[Token]) -> None:
    """Draw tables as the full report's grids: scores coloured, totals set as totals."""
    columns: list[str] = []
    column = 0

    for index, token in enumerate(tokens):
        if token.type == "table_open":
            token.attrSet("class", "grid")
            columns = []
        elif token.type == "th_open":
            columns.append(tokens[index + 1].content)
        elif token.type == "tr_open":
            column = 0
            cell = tokens[index + 2] if tokens[index + 1].type == "td_open" else None
            if cell is not None and cell.content.strip() == "**Total**":
                token.attrSet("class", "total")
        elif token.type == "td_open":
            header = columns[column] if column < len(columns) else ""
            content = tokens[index + 1].content.strip()
            band = _score_band(content) if _SCORED_COLUMN.search(header) and _SCORE.fullmatch(content) else None
            if band:
                token.attrSet("class", f"sev sev-{band.lower()}")
            column += 1


def _github_anchor(text: str) -> str:
    """The anchor GitHub gives a heading, so the links a summary makes to itself still land."""
    return re.sub(r"[^\w\- ]", "", text.strip().lower()).replace(" ", "-")


def _unique(anchor: str, taken: set[str]) -> str:
    """The anchor, numbered as GitHub numbers a second heading of the same name."""
    candidate, number = anchor or "section", 0
    while candidate in taken:
        number += 1
        candidate = f"{anchor}-{number}"
    taken.add(candidate)

    return candidate


def _slug(text: str) -> str:
    """A name fit for a file."""
    return "" if text == UNKNOWN else re.sub(r"[^a-z0-9]+", "-", text.lower()).strip("-")