#!/usr/bin/env python3
# file: scripts/audit_rust_export_completeness.py
# version: 4

"""Audit missing crate-root exports and replaceable long internal paths.

The audit resolves explicit transitive `self::` re-exports through private
module façades. Crate-root files are excluded from long-path findings because
re-export declarations must name their source module.
"""

from __future__ import annotations

import argparse
import dataclasses
import pathlib
import re
import sys


@dataclasses.dataclass(frozen=True)
class Candidate:
    """One export-completeness candidate."""

    code: str
    path: str
    line: int
    message: str


@dataclasses.dataclass(frozen=True)
class Declaration:
    """One module-level public or crate-public declaration."""

    module: str
    name: str
    visibility: str
    path: pathlib.Path
    line: int


def crate_roots(root: pathlib.Path) -> list[pathlib.Path]:
    """Return workspace crate directories that contain a Rust crate root."""

    crates: list[pathlib.Path] = []
    for manifest in root.glob("*/Cargo.toml"):
        crate = manifest.parent
        if (crate / "src/lib.rs").is_file() or (crate / "src/main.rs").is_file():
            crates.append(crate)
    return sorted(crates)


def module_path(crate: pathlib.Path, path: pathlib.Path) -> str:
    """Return the Rust module path represented by one source file."""

    relative = path.relative_to(crate / "src").with_suffix("")
    return "::".join(relative.parts)


def declaration_candidates(crate: pathlib.Path, path: pathlib.Path) -> list[Declaration]:
    """Return module-level public declarations from one Rust module."""

    text = path.read_text(encoding="utf-8")
    depth = 0
    found: list[Declaration] = []
    pattern = re.compile(
        r"^\s*(pub(?:\(crate\))?)\s+(?:(?:async|unsafe|const)\s+)*(?:const|static|type|struct|enum|trait|union|fn)\s+([A-Za-z_][A-Za-z0-9_]*)"
    )
    for number, line in enumerate(text.splitlines(), 1):
        if depth == 0:
            match = pattern.match(line)
            if match is not None:
                found.append(
                    Declaration(
                        module_path(crate, path),
                        match.group(2),
                        match.group(1),
                        path,
                        number,
                    )
                )
        depth += line.count("{") - line.count("}")
        if depth < 0:
            depth = 0
    return found


def transitive_root_exports(crate: pathlib.Path) -> dict[tuple[str, str], str]:
    """Return declarations that reach the crate root through explicit re-exports."""

    edges: dict[tuple[str, str], set[tuple[str, str]]] = {}
    pattern = re.compile(
        r"^\s*pub(?:\(crate\))?\s+use\s+self::([A-Za-z_][A-Za-z0-9_:]*)::([A-Za-z_][A-Za-z0-9_]*)\s*;",
        re.MULTILINE,
    )
    for path in sorted((crate / "src").rglob("*.rs")):
        current = "" if path.name in {"lib.rs", "main.rs"} else module_path(crate, path)
        for match in pattern.finditer(path.read_text(encoding="utf-8")):
            source_module = "::".join(part for part in (current, match.group(1)) if part)
            source = (source_module, match.group(2))
            destination = (current, match.group(2))
            edges.setdefault(source, set()).add(destination)
    resolved: dict[tuple[str, str], str] = {}
    for source in edges:
        pending = [source]
        visited: set[tuple[str, str]] = set()
        while pending:
            candidate = pending.pop()
            if candidate in visited:
                continue
            visited.add(candidate)
            if candidate[0] == "":
                resolved[source] = candidate[1]
                break
            pending.extend(edges.get(candidate, set()))
    return resolved


def audit_crate(workspace: pathlib.Path, crate: pathlib.Path) -> list[Candidate]:
    """Audit one crate and return advisory candidates."""

    crate_root = crate / "src/lib.rs"
    if not crate_root.is_file():
        crate_root = crate / "src/main.rs"
    exports = transitive_root_exports(crate)
    candidates: list[Candidate] = []
    declarations: dict[tuple[str, str], Declaration] = {}
    for path in sorted((crate / "src").rglob("*.rs")):
        if path == crate_root:
            continue
        for declaration in declaration_candidates(crate, path):
            key = (declaration.module, declaration.name)
            declarations[key] = declaration
            if key not in exports:
                relative = path.relative_to(workspace).as_posix()
                candidates.append(
                    Candidate(
                        "EXPORT001",
                        relative,
                        declaration.line,
                        f"{declaration.visibility} `{declaration.name}` has no crate-root re-export",
                    )
                )
    long_path = re.compile(
        r"\bcrate::([A-Za-z_][A-Za-z0-9_:]*)::([A-Za-z_][A-Za-z0-9_]*)"
    )
    for path in sorted((crate / "src").rglob("*.rs")):
        if path == crate_root:
            continue
        for number, line in enumerate(path.read_text(encoding="utf-8").splitlines(), 1):
            for match in long_path.finditer(line):
                key = (match.group(1), match.group(2))
                alias = exports.get(key)
                if alias is None:
                    continue
                relative = path.relative_to(workspace).as_posix()
                candidates.append(
                    Candidate(
                        "EXPORT002",
                        relative,
                        number,
                        f"long internal path `crate::{match.group(1)}::{match.group(2)}` must use `crate::{alias}`",
                    )
                )
    return candidates


def main() -> int:
    """Run the export-completeness audit."""

    parser = argparse.ArgumentParser()
    parser.add_argument("--root", default=".")
    parser.add_argument("--report-only", action="store_true")
    parser.add_argument("--summary-only", action="store_true")
    arguments = parser.parse_args()
    workspace = pathlib.Path(arguments.root).resolve()
    candidates = [item for crate in crate_roots(workspace) for item in audit_crate(workspace, crate)]
    candidates.sort(key=lambda item: (item.code, item.path, item.line, item.message))
    counts: dict[str, int] = {}
    for item in candidates:
        counts[item.code] = counts.get(item.code, 0) + 1
    sys.stdout.write(f"Rust export completeness audit: {len(candidates)} candidate(s)\n")
    for code in sorted(counts):
        sys.stdout.write(f"{code}: {counts[code]}\n")
    if not arguments.summary_only:
        for item in candidates:
            sys.stdout.write(f"{item.code} {item.path}:{item.line}: {item.message}\n")
    return 0 if arguments.report_only or not candidates else 1


if __name__ == "__main__":
    raise SystemExit(main())