#!/usr/bin/env python3
"""
extract_api.py
Scan C++ headers in ./src for public interfaces (public class/struct methods
and free function declarations) and emit markdown snippets mirroring the src/
tree into ./docs.

Each interface line is rendered as:
### `signature`

Usage:
  cd dofs
  python3 tools/extract_api.py
"""

import re
import sys
from pathlib import Path

REPO_ROOT = Path(__file__).resolve().parents[1]
SRC_DIR   = REPO_ROOT / "src"
DOCS_DIR  = REPO_ROOT / "docs"

HEADER_EXTS = {".h", ".hh", ".hpp", ".hxx"}

# ---------- Utilities ----------

def read_text(p: Path) -> str:
    try:
        return p.read_text(encoding="utf-8", errors="ignore")
    except Exception as e:
        print(f"[WARN] failed reading {p}: {e}", file=sys.stderr)
        return ""

def strip_comments(code: str) -> str:
    # Remove /* ... */ (including multiline) and // ... to end of line
    no_block = re.sub(r"/\*.*?\*/", "", code, flags=re.S)
    no_line  = re.sub(r"//.*?$", "", no_block, flags=re.M)
    return no_line

def collapse_ws(s: str) -> str:
    return re.sub(r"\s+", " ", s).strip()

def ensure_dir(path: Path):
    path.parent.mkdir(parents=True, exist_ok=True)

# ---------- Heuristic extractors ----------

ACCESS_RE = re.compile(r"^\s*(public|private|protected)\s*:\s*$")
CLASS_START_RE = re.compile(r"^\s*(class|struct)\s+([A-Za-z_]\w*)\b")
POSSIBLE_FUNC_DECL_RE = re.compile(
    r"""^[^;{}()]*\b
        (?!typedef\b)(?!using\b)(?!friend\b)
        [A-Za-z_~]\w*\s*
        \(
        [^;]*              # params
        \)
        (?:\s*(?:const|noexcept|override|final|=0|=\s*default|=\s*delete))*\s*
        ;
        \s*$""",
    re.X,
)
POSSIBLE_INLINE_DEF_RE = re.compile(
    r"""^[^;{}()]*\b
        (?!typedef\b)(?!using\b)(?!friend\b)
        [A-Za-z_~]\w*\s*
        \(
        [^{;]*              # params
        \)
        (?:\s*(?:const|noexcept|override|final))*\s*
        \{""",
    re.X,
)
SKIP_PREFIXES = ("#define", "#include", "static_assert", "enum ", "enum class ",
                 "template<", "namespace ", "using ", "typedef ", "friend ",
                 "struct ", "class ")

def extract_public_methods(lines, is_struct_default_public: bool):
    public = is_struct_default_public
    out = []
    depth = 0
    for raw in lines:
        line = raw.strip()
        if not line:
            continue

        # Track nested braces to avoid confusing nested scopes
        depth += raw.count("{")
        depth -= raw.count("}")

        m = ACCESS_RE.match(line)
        if m and depth >= 0:
            public = (m.group(1) == "public")
            continue

        if not public:
            continue

        if line.startswith(SKIP_PREFIXES) or line.endswith(":"):
            continue

        if POSSIBLE_FUNC_DECL_RE.match(line):
            out.append(collapse_ws(line))
            continue

        if POSSIBLE_INLINE_DEF_RE.match(line):
            sig = line.split("{", 1)[0].rstrip()
            out.append(collapse_ws(sig) + " { ... }")
            continue

    return out

def extract_free_function_decls(code: str):
    # Remove class/struct bodies to avoid capturing methods
    scrubbed = []
    toks = code.splitlines()
    in_class = False
    brace_balance = 0
    for line in toks:
        if not in_class:
            if CLASS_START_RE.match(line):
                in_class = True
                brace_balance = line.count("{") - line.count("}")
                scrubbed.append("")
                continue
        else:
            brace_balance += line.count("{") - line.count("}")
            if brace_balance <= 0:
                in_class = False
            scrubbed.append("")
            continue
        scrubbed.append(line)

    text = "\n".join(scrubbed)

    out = []
    for raw in text.splitlines():
        line = raw.strip()
        if not line or line.startswith(SKIP_PREFIXES):
            continue
        if POSSIBLE_FUNC_DECL_RE.match(line):
            out.append(collapse_ws(line))
        elif POSSIBLE_INLINE_DEF_RE.match(line):
            sig = line.split("{", 1)[0].rstrip()
            out.append(collapse_ws(sig) + " { ... }")
    return out

def split_top_level_classes(code: str):
    lines = code.splitlines()
    results = []
    i = 0
    while i < len(lines):
        m = CLASS_START_RE.match(lines[i])
        if not m:
            i += 1
            continue
        kind, name = m.group(1), m.group(2)
        # Find opening brace on same or subsequent lines
        j = i
        if "{" not in lines[j]:
            j += 1
            while j < len(lines) and "{" not in lines[j]:
                j += 1
            if j >= len(lines):
                i += 1
                continue
        # Capture until matching close
        depth = 0
        body = []
        while j < len(lines):
            depth += lines[j].count("{")
            depth -= lines[j].count("}")
            body.append(lines[j])
            if depth <= 0 and "}" in lines[j]:
                break
            j += 1
        body_inner = body[1:-1] if body else []
        results.append((name, kind == "struct", body_inner))
        i = j + 1
    return results

# ---------- Main per-file processing ----------

def process_header(path: Path):
    raw = read_text(path)
    if not raw:
        return None

    code = strip_comments(raw)

    # Collect classes
    class_entries = []
    for cname, is_struct, body in split_top_level_classes(code):
        methods = extract_public_methods(body, is_struct_default_public=is_struct)
        if methods:
            class_entries.append((cname, methods))

    # Collect free function decls
    free_funcs = extract_free_function_decls(code)

    if not class_entries and not free_funcs:
        return None

    # Build markdown with ### `signature` items
    rel = path.relative_to(SRC_DIR)
    md_lines = []
    md_lines.append(f"# {rel.as_posix()}")
    md_lines.append("")

    if free_funcs:
        md_lines.append("## Free functions")
        md_lines.append("")
        for sig in free_funcs:
            md_lines.append(f"### `{sig}`")
        md_lines.append("")

    for cname, methods in class_entries:
        md_lines.append(f"## class {cname} — public interface")
        md_lines.append("")
        for sig in methods:
            md_lines.append(f"### `{sig}`")
        md_lines.append("")

    return "\n".join(md_lines)

def write_markdown(src_header: Path, content: str):
    rel = src_header.relative_to(SRC_DIR)
    out_path = DOCS_DIR / rel
    out_path = out_path.with_suffix(".md")
    ensure_dir(out_path)
    out_path.write_text(content, encoding="utf-8")
    return out_path

def main():
    if not SRC_DIR.exists():
        print(f"[ERR] src/ not found at {SRC_DIR}", file=sys.stderr)
        sys.exit(1)

    generated = 0
    for path in SRC_DIR.rglob("*"):
        if not path.is_file():
            continue
        if path.suffix.lower() not in HEADER_EXTS:
            continue
        result = process_header(path)
        if result:
            out = write_markdown(path, result)
            generated += 1
            print(f"[OK] {out.relative_to(REPO_ROOT)}")

    if generated == 0:
        print("[INFO] no public interfaces detected (heuristics may have filtered everything)]")

if __name__ == "__main__":
    main()