#!/usr/bin/env python3
"""Generate a category overview Markdown file from per-item YAML frontmatter.

Reads `scripts/overview_config.yml`, picks the block named by `--category`,
walks `source_dir/*.md` (excluding `output_file`), validates each file's
frontmatter, and writes a grouped+sorted table to `output_file`.

Exits non-zero on any schema violation. Deterministic, offline, stdlib + PyYAML.
"""

from __future__ import annotations

import argparse
import re
import sys
from pathlib import Path

import yaml

REPO_ROOT = Path(__file__).resolve().parent.parent
CONFIG_PATH = REPO_ROOT / "scripts" / "overview_config.yml"

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

# Shown at the bottom of every error report so a newcomer knows where to look.
GUIDE_URL = "https://docs.makerfloss.eu/guides/editing-hardware-docs/"


class SchemaError(Exception):
    pass


def _allowed_hint(field: str, enums: dict) -> str:
    allowed = enums.get(field)
    return f" Allowed values: {', '.join(map(str, allowed))}." if allowed else ""


def _example_value(field: str, enums: dict) -> str:
    allowed = enums.get(field)
    return str(allowed[0]) if allowed else "..."


def report_errors(errors: list[str], category: str) -> None:
    """Print a collected list of problems with orientation for newcomers."""
    print(
        f"\ngen_overview: found {len(errors)} problem(s) in the {category} docs:",
        file=sys.stderr,
    )
    for err in errors:
        print(f"  ✗ {err}", file=sys.stderr)
    print(
        "\nFix the field(s) named above, then run 'make docs-index' again.\n"
        f"Guide: {GUIDE_URL}",
        file=sys.stderr,
    )


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


def validate(path: Path, fm: dict, cfg: dict) -> None:
    enums = cfg.get("enums", {})
    name = path.name
    for field in cfg["required_fields"]:
        if field not in fm:
            raise SchemaError(
                f"{name}: missing required field '{field}'. Add a line like "
                f"'{field}: {_example_value(field, enums)}' to the frontmatter."
                f"{_allowed_hint(field, enums)}"
            )
    for field, allowed in enums.items():
        if field in fm and fm[field] not in allowed:
            raise SchemaError(
                f"{name}: {field} {fm[field]!r} is not allowed. "
                f"Use one of: {', '.join(map(str, allowed))}."
            )
    key_field = cfg.get("key_field", "hostname")
    if key_field not in fm:
        raise SchemaError(
            f"{name}: missing the '{key_field}' field (the device's id). It must "
            f"match the filename, e.g. '{key_field}: {path.stem}'."
        )
    stem = path.stem
    value = fm[key_field]
    if stem != value:
        raise SchemaError(
            f"{name}: '{key_field}: {value}' does not match the filename '{name}'. "
            f"Rename the file to '{value}.md', or set {key_field} to '{stem}'."
        )


def fmt_cpu(fm: dict) -> str:
    model = fm.get("cpu") or ""
    cores = fm.get("cpu_cores")
    threads = fm.get("cpu_threads")
    suffix = ""
    if isinstance(cores, int) and isinstance(threads, int) and threads != cores:
        suffix = f" · {cores}c/{threads}t"
    elif isinstance(cores, int):
        suffix = f" · {cores}c"
    return (str(model) + suffix).strip()


def fmt_ram(fm: dict) -> str:
    n = fm.get("ram_gb")
    if isinstance(n, int):
        return f"{n} GB"
    if isinstance(n, str) and n:
        return n
    return ""


def _fmt_size_gb(n: int) -> str:
    if n >= 1000 and n % 1000 == 0:
        return f"{n // 1000} TB"
    if n >= 1000:
        return f"{n / 1000:.1f} TB"
    return f"{n} GB"


def fmt_storage(fm: dict) -> str:
    drives = fm.get("storage")
    if isinstance(drives, list) and drives:
        parts = []
        for d in drives:
            gb = d.get("gb")
            t = (d.get("type") or "").upper()
            if isinstance(gb, int):
                parts.append(f"{_fmt_size_gb(gb)} {t}".strip())
            elif t:
                parts.append(t)
        return " + ".join(parts)
    if isinstance(drives, str) and drives:
        return drives

    n = fm.get("storage_gb")
    t = fm.get("storage_type", "").upper() if fm.get("storage_type") else ""
    if not isinstance(n, int):
        return t  # type alone if no capacity
    return f"{_fmt_size_gb(n)} {t}".strip()


def fmt_nic(fm: dict) -> str:
    g = fm.get("nic_gbps")
    if g is None or g == "":
        return ""
    if isinstance(g, str):
        return g

    def one(v: float | int) -> str:
        if isinstance(v, float) and not v.is_integer():
            return f"{v}"
        return f"{int(v)}"

    if isinstance(g, list):
        if not g:
            return ""
        return "/".join(one(v) for v in g) + " GbE"
    return f"{one(g)} GbE"


def cell(fm: dict, col: dict) -> str:
    kind = col.get("kind")
    if kind == "key-link":
        v = fm[col["field"]]
        return f"[{v}]({v}.md)"
    if kind == "url-link":
        u = fm.get(col["field"], "")
        if not u:
            return ""
        label = u.removeprefix("https://").removeprefix("http://")
        return f"[{label}]({u})"
    if kind == "cpu":
        return fmt_cpu(fm)
    if kind == "ram":
        return fmt_ram(fm)
    if kind == "storage":
        return fmt_storage(fm)
    if kind == "nic":
        return fmt_nic(fm)
    value = fm.get(col["field"], "")
    return "" if value is None else str(value)


def render(cfg: dict, items: list[dict]) -> str:
    columns = cfg["columns"]
    group_by = cfg.get("group_by")
    sort_by = cfg.get("sort_by", "hostname")
    group_titles = cfg.get("group_titles", {})

    if group_by:
        groups: dict[str, list[dict]] = {}
        for fm in items:
            groups.setdefault(fm.get(group_by, ""), []).append(fm)
        ordered = sorted(groups.items())
    else:
        ordered = [("", items)]

    lines: list[str] = []
    lines.append(f"# {cfg['title']}")
    lines.append("")
    lines.append(
        f"_Auto-generated from `{cfg['source_dir']}/*.md` — do not edit by hand. "
        f"Run `make docs-index` after changing a file._"
    )
    lines.append("")

    for group_key, rows in ordered:
        rows.sort(key=lambda r: r.get(sort_by, ""))
        if group_by:
            title = group_titles.get(group_key, group_key.title() + "s")
            lines.append(f"## {title}")
            lines.append("")
        header = "| " + " | ".join(c["header"] for c in columns) + " |"
        sep = "|" + "|".join("---" for _ in columns) + "|"
        lines.append(header)
        lines.append(sep)
        for fm in rows:
            lines.append("| " + " | ".join(cell(fm, c) for c in columns) + " |")
        lines.append("")

    return "\n".join(lines).rstrip() + "\n"


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__.splitlines()[0])
    parser.add_argument("--category", required=True, help="Category key from overview_config.yml")
    args = parser.parse_args()

    config_all = yaml.safe_load(CONFIG_PATH.read_text(encoding="utf-8"))
    if args.category not in config_all:
        print(f"ERROR: category {args.category!r} not in {CONFIG_PATH}", file=sys.stderr)
        return 2
    cfg = config_all[args.category]

    source_dir = REPO_ROOT / cfg["source_dir"]
    output_file = REPO_ROOT / cfg["output_file"]
    output_abs = output_file.resolve()

    items: list[dict] = []
    errors: list[str] = []
    for path in sorted(source_dir.glob("*.md")):
        if path.resolve() == output_abs:
            continue
        try:
            fm = parse_frontmatter(path)
        except SchemaError as e:
            errors.append(str(e))
            continue
        if fm is None:
            print(
                f"WARNING: {path.name}: no '---' frontmatter block — skipping "
                f"(it will not appear in the {args.category} index).",
                file=sys.stderr,
            )
            continue
        try:
            validate(path, fm, cfg)
        except SchemaError as e:
            errors.append(str(e))
            continue
        items.append(fm)

    if errors:
        report_errors(errors, args.category)
        return 1

    output_file.parent.mkdir(parents=True, exist_ok=True)
    tmp = output_file.with_suffix(output_file.suffix + ".tmp")
    tmp.write_text(render(cfg, items), encoding="utf-8")
    tmp.replace(output_file)
    print(f"Wrote {output_file.relative_to(REPO_ROOT)} ({len(items)} item(s))")
    return 0


if __name__ == "__main__":
    sys.exit(main())