#!/usr/bin/env python3
"""Generates libs/relax/front/src/feature_tables.rs from rustc 1.97.1's rustc_feature crate.

    python3 feature_tables.py <rust-src>/compiler/rustc_feature/src > ../src/feature_tables.rs

Sources: unstable.rs (ACTIVE lang features), accepted.rs, removed.rs, builtin_attrs.rs
(BUILTIN_ATTRIBUTES: the gated entries and GATED_CFGS).
"""
import re, sys

src = sys.argv[1]


def read(n):
    return open(src + "/" + n).read()


def feats(text, kind):
    out = []
    for m in re.finditer(r"^\s*\(%s,\s*(\w+),\s*\"([^\"]*)\"" % kind, text, re.M):
        out.append((m.group(1), m.group(2)))
    return out


def rs(s):
    return '"' + s.replace("\\", "\\\\").replace('"', '\\"') + '"'


def args_of(text, start):
    """The top-level comma separated arguments of the macro call whose '(' is at text[start]."""
    depth, i, cur, out, instr = 0, start, [], [], False
    while i < len(text):
        c = text[i]
        if instr:
            cur.append(c)
            if c == "\\":
                cur.append(text[i + 1]); i += 1
            elif c == '"':
                instr = False
        elif c == '"':
            instr = True; cur.append(c)
        elif c in "([":
            depth += 1
            if depth > 1: cur.append(c)
        elif c in ")]":
            depth -= 1
            if depth == 0:
                out.append("".join(cur).strip()); return out, i
            cur.append(c)
        elif c == "," and depth == 1:
            out.append("".join(cur).strip()); cur = []
        else:
            cur.append(c)
        i += 1
    raise SystemExit("unbalanced")


def lit(s):
    """Value of a Rust string literal / experimental!(x) / concat!(..) argument."""
    s = s.strip()
    m = re.fullmatch(r"experimental!\((\w+)\)", s)
    if m:
        return "the `#[%s]` attribute is an experimental feature" % m.group(1)
    if s.startswith("concat!"):
        return None
    assert s.startswith('"') and s.endswith('"'), s
    body = s[1:-1]
    body = re.sub(r"\\\n\s*", "", body)
    return body.replace('\\"', '"').replace("\\\\", "\\")


unstable = feats(read("unstable.rs"), "unstable") + feats(read("unstable.rs"), "incomplete") + feats(read("unstable.rs"), "internal")
accepted = feats(read("accepted.rs"), "accepted")
removed = feats(read("removed.rs"), "removed")

battr = read("builtin_attrs.rs")
body = battr[battr.index("pub static BUILTIN_ATTRIBUTES"):]
body = re.sub(r"(?m)^\s*//.*$", "", body)
body = re.sub(r"(?m)\s//[^\"\n]*$", "", body)
gated = []  # (attr, feature, message)
for m in re.finditer(r"^\s*(gated|rustc_attr)!\(", body, re.M):
    kind = m.group(1)
    args, _ = args_of(body, m.end() - 1)
    if kind == "gated":
        name = args[0]
        if len(args) >= 3 and re.fullmatch(r"\w+", args[1]):
            feat, msg = args[1], lit(args[2])
        else:
            feat, msg = name, lit(args[1])
    else:
        if args[0] == "TEST":
            name = args[1]
        else:
            name = args[0]
        feat, msg = "rustc_attrs", "use of an internal attribute"
    gated.append((name, feat, msg))
gated.append(("rustc_diagnostic_item", "rustc_attrs", "use of an internal attribute"))
gated.sort()

gcfg = []
g = battr[battr.index("const GATED_CFGS"):battr.index("/// Find a gated cfg")]
for m in re.finditer(r"\(\s*sym::(\w+),\s*sym::(\w+),", g):
    gcfg.append((m.group(1), m.group(2)))

o = []
o.append("// @generated by libs/relax/front/gen/feature_tables.py from rustc 1.97.1 rustc_feature; do not edit.")
o.append("")
o.append("/// ACTIVE lang features (unstable.rs), by name.")
o.append("pub static UNSTABLE: &[&str] = &[")
for n, _ in unstable: o.append("    %s," % rs(n))
o.append("];\n")
o.append("/// ACCEPTED lang features (accepted.rs): name, stable since.")
o.append("pub static ACCEPTED: &[(&str, &str)] = &[")
for n, v in accepted: o.append("    (%s, %s)," % (rs(n), rs(v)))
o.append("];\n")
o.append("/// REMOVED lang features (removed.rs): name.")
o.append("pub static REMOVED: &[&str] = &[")
for n, _ in removed: o.append("    %s," % rs(n))
o.append("];\n")
o.append("/// The gated entries of BUILTIN_ATTRIBUTES: attribute, feature, message.")
o.append("pub static GATED_ATTRS: &[(&str, &str, &str)] = &[")
for n, f, m in gated: o.append("    (%s, %s, %s)," % (rs(n), rs(f), rs(m)))
o.append("];\n")
o.append("/// GATED_CFGS: cfg name, feature.")
o.append("pub static GATED_CFGS: &[(&str, &str)] = &[")
for n, f in gcfg: o.append("    (%s, %s)," % (rs(n), rs(f)))
o.append("];")
print("\n".join(o))