#!/usr/bin/env python3
"""Generate the C++ punctuation contract from policy.json."""
import argparse
import json
from pathlib import Path

ROOT = Path(__file__).resolve().parent
SPEC = json.loads((ROOT / "policy.json").read_text(encoding="utf-8"))
simple = SPEC["simple"]
alternating = SPEC["alternating"]
nested = SPEC["nested"]
inputs = [entry["input"] for entry in simple + alternating] + [nested["openingInput"], nested["closingInput"]]
if (SPEC["contractVersion"] != 1 or any(len(value) != 1 or not 32 <= ord(value) < 127 for value in inputs) or
        len(set(inputs)) != len(inputs)):
    raise SystemExit("Invalid punctuation contract")


def char_literal(value):
    return "'" + value.replace("\\", "\\\\").replace("'", "\\'") + "'"

lines = [
    "// Generated by contracts/punctuation/generate.py; edit policy.json instead.",
    "#pragma once",
    "#include <array>",
    "#include <string_view>",
    "",
    "namespace metasequoia::punctuation_contract",
    "{",
    f"inline constexpr int version = {SPEC['contractVersion']};",
    "struct Mapping",
    "{",
    "    char input;",
    "    const char *output;",
    "};",
    "struct AlternatingMapping",
    "{",
    "    char input;",
    "    const char *opening;",
    "    const char *closing;",
    "};",
    f"inline constexpr std::array<Mapping, {len(simple)}> simple = {{{{",
]
lines += [f"    {{{char_literal(entry['input'])}, {json.dumps(entry['output'], ensure_ascii=False)}}}," for entry in simple]
lines += [
    "}};",
    f"inline constexpr std::array<AlternatingMapping, {len(alternating)}> alternating = {{{{",
]
lines += [
    f"    {{{char_literal(entry['input'])}, {json.dumps(entry['opening'], ensure_ascii=False)}, {json.dumps(entry['closing'], ensure_ascii=False)}}},"
    for entry in alternating
]
lines += [
    "}};",
    f"inline constexpr char nested_opening_input = {char_literal(nested['openingInput'])};",
    f"inline constexpr char nested_closing_input = {char_literal(nested['closingInput'])};",
    f"inline constexpr char nested_opening[] = {json.dumps(nested['opening'], ensure_ascii=False)};",
    f"inline constexpr char nested_opening_inner[] = {json.dumps(nested['nestedOpening'], ensure_ascii=False)};",
    f"inline constexpr char nested_closing[] = {json.dumps(nested['closing'], ensure_ascii=False)};",
    f"inline constexpr char nested_closing_inner[] = {json.dumps(nested['nestedClosing'], ensure_ascii=False)};",
    "constexpr bool is_supported(char input)",
    "{",
    "    for (const auto &mapping : simple)",
    "        if (mapping.input == input) return true;",
    "    for (const auto &mapping : alternating)",
    "        if (mapping.input == input) return true;",
    "    return input == nested_opening_input || input == nested_closing_input;",
    "}",
    "constexpr const char *simple_output(char input)",
    "{",
    "    for (const auto &mapping : simple)",
    "        if (mapping.input == input) return mapping.output;",
    "    return nullptr;",
    "}",
    "constexpr const AlternatingMapping *alternating_mapping(char input)",
    "{",
    "    for (const auto &mapping : alternating)",
    "        if (mapping.input == input) return &mapping;",
    "    return nullptr;",
    "}",
    "} // namespace metasequoia::punctuation_contract",
    "",
]
expected = "\n".join(lines)

parser = argparse.ArgumentParser(description=__doc__)
parser.add_argument("--check", action="store_true")
args = parser.parse_args()
target = ROOT / "policy.h"
if args.check:
    if not target.exists() or target.read_text(encoding="utf-8") != expected:
        raise SystemExit("Punctuation contract header is stale; run contracts/punctuation/generate.py")
else:
    target.write_text(expected, encoding="utf-8")