#!/usr/bin/env python3
"""Regenerate _methods-index.md: a lineage forest over method notes.

This is NOT a taxonomy. The `family` field is coarse grouping only and each
method's real signature lives in its aspects (see Methods.md). This view just
surfaces the genealogy the lineage edges already encode: `variant-of` is the
tree spine; `refines` / `combines` are shown inline. Roots are ranked by number
of descendants so the biggest method families float to the top. A node with no
method note (ⓘ) is a lineage anchor only (a canonical method name others descend
from that has not been analyzed as its own note).

    python3 _scripts/make_methods_index.py
"""
import glob
import os
import re
from collections import defaultdict, Counter

VAULT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


def fm_field(text, name):
    parts = text.split("---")
    if len(parts) < 2:
        return ""
    m = re.search(rf'^{name}:[ \t]*([^#\n]*)', parts[1], flags=re.M)  # YAML: `# ...` is a comment
    return m.group(1).strip().strip('"') if m else ""


def edge_targets(text, edge):
    out = []
    for m in re.finditer(rf'^{edge}::\s*\[\[([^\]]+)\]\]', text, flags=re.M):
        out.append(m.group(1).split("|")[0].strip())
    return out


def paper_slug(text):
    m = re.search(r'^introduced-in:\s*"?\[\[([^\]]+)\]\]', text.split("---")[1], flags=re.M) \
        if len(text.split("---")) > 1 else None
    return m.group(1).strip() if m else ""


def main():
    methods = {}
    for path in sorted(glob.glob(os.path.join(VAULT, "methods", "*.md"))):
        slug = os.path.splitext(os.path.basename(path))[0]
        text = open(path, encoding="utf-8").read()
        methods[slug] = {
            "family": fm_field(text, "family"),
            "paper": paper_slug(text),
            "variant_of": edge_targets(text, "variant-of"),
            "refines": edge_targets(text, "refines"),
            "combines": edge_targets(text, "combines"),
        }

    # tree spine = first variant-of target
    parent = {}
    for s, d in methods.items():
        parent[s] = d["variant_of"][0] if d["variant_of"] else None

    nodes = set(methods) | {p for p in parent.values() if p}
    children = defaultdict(list)
    for s in methods:
        p = parent[s]
        if p:
            children[p].append(s)
    roots = sorted(n for n in nodes if not parent.get(n))

    def subtree_size(n, seen=None):
        seen = seen or set()
        if n in seen:
            return 0
        seen.add(n)
        return len(children[n]) + sum(subtree_size(c, seen) for c in children[n])

    def render(n, depth, out, seen):
        if n in seen:
            out.append("  " * depth + f"- {n} (cycle)")
            return
        seen = seen | {n}
        d = methods.get(n)
        if d:
            bits = []
            if d["paper"]:
                bits.append(f"[[{d['paper']}]]")
            if d["family"]:
                bits.append(f"·{d['family']}·")
            extra = d["variant_of"][1:]
            ann = []
            if extra:
                ann.append("also variant-of " + ", ".join(extra))
            if d["refines"]:
                ann.append("refines " + ", ".join(d["refines"]))
            if d["combines"]:
                ann.append("combines " + ", ".join(d["combines"]))
            tail = (" — " + "; ".join(ann)) if ann else ""
            out.append("  " * depth + f"- [[{n}]] {' '.join(bits)}{tail}")
        else:
            out.append("  " * depth + f"- {n} ⓘ")
        for c in sorted(children[n], key=lambda x: (-subtree_size(x), x)):
            render(c, depth + 1, out, seen)

    fam = Counter(d["family"] or "—" for d in methods.values())

    L = ["---", "tags: [meta]", "---", "", "# Methods index", "",
         "Generated by `_scripts/make_methods_index.py` — a lineage forest, **not a",
         "taxonomy**. The `family` label is coarse; a method's real signature is its",
         "aspects ([[Methods]]). `variant-of` is the tree spine; `refines`/`combines`",
         "are shown inline. Roots are ranked by descendant count. `ⓘ` = lineage anchor",
         "with no method note of its own.", "",
         "## Families (coarse)", "",
         "| Family | Methods |", "|---|---|"]
    for f, n in sorted(fam.items(), key=lambda kv: (-kv[1], kv[0])):
        L.append(f"| {f} | {n} |")
    L += ["", f"Total method notes: {len(methods)}", "",
          "## Lineage forest", ""]

    ranked = sorted(roots, key=lambda r: (-subtree_size(r), r))
    for r in ranked:
        # skip singletons (a root that is a lone method note with no children) into a tail section
        if not children[r]:
            continue
        out = []
        render(r, 0, out, set())
        L.extend(out)
        L.append("")

    singletons = sorted(r for r in ranked if r in methods and not children[r])
    if singletons:
        L += ["## Standalone methods (no lineage edges)", ""]
        for s in singletons:
            d = methods[s]
            bits = (f"[[{d['paper']}]] " if d["paper"] else "") + (f"·{d['family']}·" if d["family"] else "")
            L.append(f"- [[{s}]] {bits}")

    open(os.path.join(VAULT, "_methods-index.md"), "w", encoding="utf-8").write("\n".join(L) + "\n")
    print(f"wrote _methods-index.md: {len(methods)} methods, "
          f"{len([r for r in ranked if children[r]])} lineage trees, {len(singletons)} standalone")


if __name__ == "__main__":
    main()