#!/usr/bin/env python3
"""Discover and document the relationship between GDScript and Rust files.

Outputs a Markdown report mapping:
  1. Rust → Godot bindings exposed by `src/simulator/api-gdext/`
     (`#[derive(GodotClass)]` structs, with optional `#[class(rename=...)]`).
  2. GDScript callers of each exposed class (grep over `*.gd`).
  3. GDScript `class_name` declarations and `extends`/preload references to
     Rust-backed classes.
  4. Crate-level dependency graph for `src/simulator/crates/*` and the two
     bridge crates (`api-gdext`, `api-wasm`).

Re-runnable: `python3 tools/gd-rust-relationships.py [--out PATH]`.
"""
from __future__ import annotations

import argparse
import re
import sys
from collections import defaultdict
from dataclasses import dataclass, field
from pathlib import Path

REPO_ROOT = Path(__file__).resolve().parents[1]
SIM_ROOT = REPO_ROOT / "src" / "simulator"
GDEXT_SRC = SIM_ROOT / "api-gdext" / "src"
CRATES_DIR = SIM_ROOT / "crates"
GD_ROOTS = [REPO_ROOT / "src" / "game"]  # all .gd files live here

GODOT_CLASS_RE = re.compile(r"#\[derive\([^)]*\bGodotClass\b[^)]*\)\]")
CLASS_ATTR_RE = re.compile(r"#\[class\(([^)]*)\)\]")
RENAME_RE = re.compile(r"rename\s*=\s*([A-Za-z_][A-Za-z0-9_]*)")
BASE_RE = re.compile(r"base\s*=\s*([A-Za-z_][A-Za-z0-9_]*)")
STRUCT_RE = re.compile(r"^\s*pub\s+struct\s+([A-Za-z_][A-Za-z0-9_]*)")
FUNC_RE = re.compile(r"#\[func\]")
FN_NAME_RE = re.compile(r"\bfn\s+([A-Za-z_][A-Za-z0-9_]*)")

DEP_TABLE_RE = re.compile(r"^\[(dependencies|dev-dependencies|build-dependencies)\]")
DEP_LINE_RE = re.compile(r"^([A-Za-z0-9_\-]+)\s*=")


@dataclass
class RustClass:
    name: str            # exported name (after rename) — what Godot/GDScript sees
    rust_struct: str     # original Rust struct identifier
    base: str | None
    file: Path
    line: int
    func_count: int = 0
    callers: list[tuple[Path, int]] = field(default_factory=list)


def find_godot_classes(gdext_src: Path) -> list[RustClass]:
    classes: list[RustClass] = []
    for rs in sorted(gdext_src.rglob("*.rs")):
        text = rs.read_text(encoding="utf-8", errors="replace")
        lines = text.splitlines()
        i = 0
        while i < len(lines):
            if GODOT_CLASS_RE.search(lines[i]):
                base: str | None = None
                rename: str | None = None
                # Look ahead for #[class(...)] and pub struct
                j = i + 1
                while j < len(lines) and j < i + 12:
                    m_class = CLASS_ATTR_RE.search(lines[j])
                    if m_class:
                        attrs = m_class.group(1)
                        if (mb := BASE_RE.search(attrs)):
                            base = mb.group(1)
                        if (mr := RENAME_RE.search(attrs)):
                            rename = mr.group(1)
                    m_struct = STRUCT_RE.match(lines[j])
                    if m_struct:
                        struct_name = m_struct.group(1)
                        # Count #[func]s in the impl block by scanning forward
                        func_count = 0
                        k = j + 1
                        depth = 0
                        seen_impl = False
                        while k < len(lines):
                            ln = lines[k]
                            if f"impl {struct_name}" in ln or f"impl I" in ln and struct_name in ln:
                                seen_impl = True
                            if FUNC_RE.search(ln) and (
                                f"impl {struct_name}" in "\n".join(lines[max(0, k - 30):k])
                            ):
                                func_count += 1
                            k += 1
                            if k - j > 4000:
                                break
                        classes.append(
                            RustClass(
                                name=rename or struct_name,
                                rust_struct=struct_name,
                                base=base,
                                file=rs,
                                line=j + 1,
                                func_count=func_count,
                            )
                        )
                        i = j
                        break
                    j += 1
            i += 1
    return classes


def find_gd_files(roots: list[Path]) -> list[Path]:
    files: list[Path] = []
    for root in roots:
        if root.exists():
            files.extend(sorted(root.rglob("*.gd")))
    return files


def map_callers(classes: list[RustClass], gd_files: list[Path]) -> None:
    # Build name → class index
    by_name: dict[str, list[RustClass]] = defaultdict(list)
    for c in classes:
        by_name[c.name].append(c)
    # Word-boundary regex for all names at once (alternation)
    if not by_name:
        return
    name_re = re.compile(r"\b(" + "|".join(re.escape(n) for n in by_name) + r")\b")
    for gd in gd_files:
        try:
            text = gd.read_text(encoding="utf-8", errors="replace")
        except OSError:
            continue
        for m in name_re.finditer(text):
            n = m.group(1)
            line_no = text.count("\n", 0, m.start()) + 1
            for c in by_name[n]:
                c.callers.append((gd, line_no))


def parse_gd_class_names(gd_files: list[Path]) -> dict[str, Path]:
    out: dict[str, Path] = {}
    cn_re = re.compile(r"^\s*class_name\s+([A-Za-z_][A-Za-z0-9_]*)", re.M)
    for gd in gd_files:
        try:
            text = gd.read_text(encoding="utf-8", errors="replace")
        except OSError:
            continue
        m = cn_re.search(text)
        if m:
            out[m.group(1)] = gd
    return out


def parse_crate_deps(sim_root: Path) -> dict[str, set[str]]:
    """Return crate_name → set of in-workspace crate deps."""
    workspace_crates: set[str] = set()
    cargo_files: list[Path] = []
    for d in sorted(sim_root.glob("crates/*")):
        if (d / "Cargo.toml").is_file():
            workspace_crates.add(d.name)
            cargo_files.append(d / "Cargo.toml")
    for bridge in ("api-gdext", "api-wasm"):
        toml = sim_root / bridge / "Cargo.toml"
        if toml.is_file():
            workspace_crates.add(bridge)
            cargo_files.append(toml)

    deps: dict[str, set[str]] = {}
    for toml in cargo_files:
        text = toml.read_text(encoding="utf-8", errors="replace")
        crate_name: str | None = None
        in_pkg = False
        in_dep = False
        local_deps: set[str] = set()
        for line in text.splitlines():
            s = line.strip()
            if s.startswith("[package]"):
                in_pkg, in_dep = True, False
                continue
            if DEP_TABLE_RE.match(s):
                in_pkg, in_dep = False, True
                continue
            if s.startswith("[") and s.endswith("]"):
                # nested table like [dependencies.foo] still counts the prefix
                if s.startswith("[dependencies.") or s.startswith("[dev-dependencies."):
                    name = s.split(".", 1)[1].rstrip("]")
                    if name in workspace_crates:
                        local_deps.add(name)
                    in_pkg, in_dep = False, False
                    continue
                in_pkg, in_dep = False, False
                continue
            if in_pkg and s.startswith("name"):
                m = re.search(r'"([^"]+)"', s)
                if m:
                    crate_name = m.group(1)
            if in_dep:
                m = DEP_LINE_RE.match(s)
                if m and m.group(1) in workspace_crates:
                    local_deps.add(m.group(1))
        if crate_name:
            deps[crate_name] = local_deps
    return deps


def build_json(
    classes: list[RustClass],
    gd_classes: dict[str, Path],
    deps: dict[str, set[str]],
) -> dict:
    rust_names = {c.name for c in classes}
    return {
        "generatedAt": __import__("datetime").datetime.utcnow().isoformat() + "Z",
        "classes": [
            {
                "name": c.name,
                "rustStruct": c.rust_struct,
                "base": c.base,
                "file": str(c.file.relative_to(REPO_ROOT)),
                "line": c.line,
                "funcCount": c.func_count,
                "callerFiles": sorted(
                    {str(p.relative_to(REPO_ROOT)) for p, _ in c.callers}
                ),
                "callerLines": [
                    {"file": str(p.relative_to(REPO_ROOT)), "line": ln}
                    for p, ln in sorted(c.callers, key=lambda x: (str(x[0]), x[1]))
                ],
            }
            for c in sorted(classes, key=lambda x: x.name)
        ],
        "gdClassNames": {
            name: str(path.relative_to(REPO_ROOT))
            for name, path in sorted(gd_classes.items())
        },
        "collisions": sorted(set(gd_classes) & rust_names),
        "crateDeps": {
            crate: sorted(ds) for crate, ds in sorted(deps.items())
        },
    }


def render_report(
    classes: list[RustClass],
    gd_classes: dict[str, Path],
    deps: dict[str, set[str]],
) -> str:
    out: list[str] = []
    out.append("# GDScript ↔ Rust Relationship Report\n")
    out.append(
        f"_Generated by `tools/gd-rust-relationships.py` over `{SIM_ROOT.relative_to(REPO_ROOT)}` and `src/game/`._\n"
    )

    # 1. Bridge surface
    out.append("\n## 1. GDExtension surface (Rust → Godot)\n")
    out.append(
        f"**{len(classes)}** Godot-visible classes exported from "
        f"`src/simulator/api-gdext/`. Each row shows where the class is defined "
        "and how many `.gd` files reference it by name.\n"
    )
    out.append("| Godot class | base | `#[func]` count | GD callers | Defined in |")
    out.append("|---|---|---:|---:|---|")
    for c in sorted(classes, key=lambda x: x.name):
        rel = c.file.relative_to(REPO_ROOT)
        gd_caller_files = {p for p, _ in c.callers}
        out.append(
            f"| `{c.name}` | `{c.base or '-'}` | {c.func_count} | "
            f"{len(gd_caller_files)} | `{rel}:{c.line}` |"
        )

    # 2. Per-class GD callers
    out.append("\n## 2. Per-class GD callers\n")
    for c in sorted(classes, key=lambda x: x.name):
        gd_caller_files = sorted({p for p, _ in c.callers})
        if not gd_caller_files:
            continue
        out.append(f"\n### `{c.name}`")
        out.append(f"_Rust struct `{c.rust_struct}` in `{c.file.relative_to(REPO_ROOT)}`._")
        for p in gd_caller_files:
            lines = sorted({ln for q, ln in c.callers if q == p})
            line_str = ", ".join(f"L{ln}" for ln in lines[:8]) + (
                f", … (+{len(lines)-8})" if len(lines) > 8 else ""
            )
            out.append(f"- `{p.relative_to(REPO_ROOT)}` — {line_str}")

    # 3. Unused exports
    unused = [c for c in classes if not c.callers]
    out.append("\n## 3. Exported but unreferenced from any `.gd`\n")
    if not unused:
        out.append("_None — every exposed class has at least one GDScript reference._")
    else:
        for c in sorted(unused, key=lambda x: x.name):
            out.append(
                f"- `{c.name}` (`{c.file.relative_to(REPO_ROOT)}:{c.line}`)"
            )

    # 4. GDScript class_name registry
    out.append("\n## 4. GDScript `class_name` declarations\n")
    out.append(f"**{len(gd_classes)}** GDScript classes declare a `class_name`. "
               "Names that collide with a Rust-exported class would shadow the binding:\n")
    rust_names = {c.name for c in classes}
    collisions = sorted(set(gd_classes) & rust_names)
    if collisions:
        out.append("**⚠ Name collisions:**")
        for n in collisions:
            out.append(f"- `{n}` — GD: `{gd_classes[n].relative_to(REPO_ROOT)}` / Rust: see §1")
    else:
        out.append("_No collisions._")

    # 5. Crate dependency graph
    out.append("\n## 5. Workspace crate dependency graph\n")
    out.append("```mermaid")
    out.append("graph LR")
    for crate, ds in sorted(deps.items()):
        if not ds:
            out.append(f'  {crate.replace("-", "_")}["{crate}"]')
        for d in sorted(ds):
            out.append(
                f'  {crate.replace("-", "_")}["{crate}"] --> '
                f'{d.replace("-", "_")}["{d}"]'
            )
    out.append("```")

    # 6. api-gdext crate fan-in
    bridges = {"api-gdext", "api-wasm"}
    out.append("\n## 6. Bridge-crate fan-in\n")
    for b in sorted(bridges):
        if b in deps:
            out.append(f"\n### `{b}` depends on:")
            for d in sorted(deps[b]):
                out.append(f"- `{d}`")

    out.append("")
    return "\n".join(out)


def main() -> int:
    import json

    ap = argparse.ArgumentParser()
    ap.add_argument(
        "--out",
        type=Path,
        default=REPO_ROOT / ".project" / "reports" / "gd-rust-relationships.md",
    )
    args = ap.parse_args()
    json_out = args.out.with_suffix(".json")

    if not GDEXT_SRC.is_dir():
        print(f"error: {GDEXT_SRC} not found", file=sys.stderr)
        return 1

    classes = find_godot_classes(GDEXT_SRC)
    gd_files = find_gd_files(GD_ROOTS)
    map_callers(classes, gd_files)
    gd_classes = parse_gd_class_names(gd_files)
    deps = parse_crate_deps(SIM_ROOT)

    args.out.parent.mkdir(parents=True, exist_ok=True)
    args.out.write_text(render_report(classes, gd_classes, deps), encoding="utf-8")
    json_out.write_text(
        json.dumps(build_json(classes, gd_classes, deps), indent=2), encoding="utf-8"
    )

    referenced = sum(1 for c in classes if c.callers)
    print(
        f"Scanned {len(classes)} Godot-exposed Rust classes across "
        f"{len(list(GDEXT_SRC.rglob('*.rs')))} api-gdext files; "
        f"{referenced} referenced from {len(gd_files)} .gd files. "
        f"Crates: {len(deps)}. "
        f"Markdown: {args.out.relative_to(REPO_ROOT)}  JSON: {json_out.relative_to(REPO_ROOT)}"
    )
    return 0


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