#!/usr/bin/env python3
"""Generate per-rack elevation SVG + page from hardware frontmatter.

Reads `docs/hardware/*.md`, selects files that declare a `rack` field,
validates rack placement, and writes for each rack:
  docs/infrastructure/racks/<rack>-elevation.svg
  docs/infrastructure/racks/<rack>.md

Deterministic, offline, stdlib + PyYAML. Non-zero exit on schema violation.
The physical rack is labeled U1 at the top; the SVG renders U1 at the top.
"""

from __future__ import annotations

import re
import sys
from pathlib import Path

import yaml

REPO_ROOT = Path(__file__).resolve().parent.parent
HARDWARE_DIR = REPO_ROOT / "docs" / "hardware"
OUTPUT_DIR = REPO_ROOT / "docs" / "infrastructure" / "racks"
RACK_UNITS = 48

FRONTMATTER_RE = re.compile(r"^---\s*\n(.*?)\n---\s*\n", re.DOTALL)

FACES = {"front", "rear", "both", "left", "right"}
ZERO_U_FACES = {"left", "right"}

KIND_COLORS = {
    "server": "#4c78a8",
    "switch": "#59a14f",
    "patch-panel": "#9c755f",
    "pdu": "#e15759",
    "ups": "#edc948",
    "shelf": "#bab0ac",
    "kvm": "#b07aa1",
    "blank": "#d4d4d4",
}
DEFAULT_COLOR = "#888888"


class SchemaError(Exception):
    pass


def parse_frontmatter(path: Path) -> dict | None:
    text = path.read_text(encoding="utf-8")
    m = FRONTMATTER_RE.match(text)
    if not m:
        return None
    data = yaml.safe_load(m.group(1))
    if not isinstance(data, dict):
        raise SchemaError(f"{path}: frontmatter is not a mapping")
    return data


def load_rack_items(hardware_dir: Path) -> list[dict]:
    """Return frontmatter dicts for hardware files that declare a rack."""
    items: list[dict] = []
    for path in sorted(hardware_dir.glob("*.md")):
        if path.name == "index.md":
            continue
        fm = parse_frontmatter(path)
        if fm is None or "rack" not in fm:
            continue
        fm = dict(fm)
        fm["_path"] = str(path)
        items.append(fm)
    return items


def validate_item(fm: dict) -> None:
    name = fm.get("hostname") or fm.get("_path", "?")
    face = fm.get("rack_face")
    if face not in FACES:
        raise SchemaError(f"{name}: rack_face={face!r} not in {sorted(FACES)}")
    if face in ZERO_U_FACES:
        if "rack_u" in fm or "u_height" in fm:
            raise SchemaError(
                f"{name}: 0U item (face={face}) must omit rack_u/u_height"
            )
        return
    u = fm.get("rack_u")
    h = fm.get("u_height")
    if not isinstance(u, int) or not isinstance(h, int):
        raise SchemaError(f"{name}: rack_u and u_height must be integers")
    if u < 1 or u > RACK_UNITS:
        raise SchemaError(f"{name}: rack_u={u} out of range 1..{RACK_UNITS}")
    if h < 1:
        raise SchemaError(f"{name}: u_height={h} must be >= 1")
    if u + h - 1 > RACK_UNITS:
        raise SchemaError(
            f"{name}: occupies U{u}..U{u + h - 1}, exceeds {RACK_UNITS}U"
        )