#!/usr/bin/env python3
"""Generate UGI_GRAMMAR_v0.ebnf from ugi_registry_v0.json."""

import json
import os
import sys


def load_registry(path):
    with open(path, "r") as f:
        return json.load(f)


def main():
    if len(sys.argv) != 3:
        print(f"Usage: {sys.argv[0]} <registry.json> <output.ebnf>", file=sys.stderr)
        sys.exit(1)

    registry_path, output_path = sys.argv[1], sys.argv[2]
    reg = load_registry(registry_path)
    fields = reg["fields"]

    lines = []
    lines.append("/* UGI Grammar v0: W3C EBNF */")
    lines.append("/* Generated from ugi_registry_v0.json */")
    lines.append("/* Compatible with bottlecaps.de/rr/ui */")
    lines.append("")

    # ── Top-level ──
    lines.append("/* === Top-level === */")
    lines.append("")
    lines.append("ugi_string ::= 'ugi:' version '@' handle ':' field_list")
    lines.append("")
    lines.append("version ::= digit+ ( '/' digit+ )?")
    lines.append("")
    lines.append("/* handle: alphanumeric, hyphens, underscores, dots */")
    lines.append("handle ::= ( alpha | digit | '-' | '_' | '.' )+")
    lines.append("")
    lines.append("field_list ::= field ( ',' field )*")
    lines.append("")

    # ── Field dispatch ──
    lines.append("/* === Field dispatch === */")
    lines.append("")

    field_alts = [f"field_{code}" for code in sorted(fields.keys())]
    # Break into multiple lines for readability
    lines.append("field ::= " + "\n       | ".join(field_alts))
    lines.append("")

    # ── Common rules ──
    lines.append("/* === Common rules === */")
    lines.append("")
    lines.append("odigit ::= [0-7]")
    lines.append("")
    lines.append("paid ::= '$'")
    lines.append("")
    lines.append("aspire ::= '+' odigit")
    lines.append("")
    lines.append("paid_aspire ::= paid aspire?")
    lines.append("")
    lines.append("modifier ::= paid_aspire | aspire")
    lines.append("")
    lines.append("alternative ::= '/' odigit")
    lines.append("")
    lines.append("/* custom sub-ID: ~ followed by 2+ alpha chars */")
    lines.append("custom_sub ::= '~' alpha alpha alpha*")
    lines.append("")
    lines.append("/* sub-ID: 1-4 alpha chars */")
    lines.append("sub_id ::= alpha alpha? alpha? alpha?")
    lines.append("")

    # ── Per-field rules ──
    lines.append("/* === Per-field rules === */")
    lines.append("")

    for code in sorted(fields.keys()):
        f = fields[code]
        ftype = f["type"]
        mods = f.get("modifiers", {})
        has_paid = mods.get("paid", False)
        has_aspire = mods.get("aspire", False)
        has_alt = mods.get("alternative", False)

        lines.append(f"/* {code}: {f['name']} ({ftype}) */")

        if ftype == "direct":
            mod_parts = []
            if has_alt:
                mod_parts.append("alternative")
            if has_paid and has_aspire:
                mod_parts.append("modifier")
            elif has_paid:
                mod_parts.append("paid")
            elif has_aspire:
                mod_parts.append("aspire")

            if mod_parts:
                mod_str = " ( " + " | ".join(mod_parts) + " )?"
            else:
                mod_str = ""

            lines.append(f"field_{code} ::= '{code}' odigit{mod_str}")

        elif ftype == "multi":
            mod_parts = []
            if has_paid and has_aspire:
                mod_parts.append("modifier")
            elif has_paid:
                mod_parts.append("paid")
            elif has_aspire:
                mod_parts.append("aspire")

            if mod_parts:
                mod_str = " ( " + " | ".join(mod_parts) + " )?"
            else:
                mod_str = ""

            if code == "l":
                # l uses 2-char ISO 639-1 codes instead of generic sub-ids
                lines.append(
                    f"field_{code}_entry ::= alpha alpha odigit{mod_str}"
                )
            else:
                lines.append(
                    f"field_{code}_entry ::= ( sub_id | custom_sub ) odigit{mod_str}"
                )
            lines.append(
                f"field_{code} ::= '{code}' field_{code}_entry+"
            )

        elif ftype == "single":
            mod_parts = []
            if has_paid and has_aspire:
                mod_parts.append("modifier")
            elif has_paid:
                mod_parts.append("paid")
            elif has_aspire:
                mod_parts.append("aspire")

            if mod_parts:
                mod_str = " ( " + " | ".join(mod_parts) + " )?"
            else:
                mod_str = ""

            lines.append(
                f"field_{code} ::= '{code}' ( sub_id | custom_sub ) odigit{mod_str}"
            )

        elif ftype == "special":
            if code == "g":
                lines.append("g_domain ::= alpha alpha alpha? alpha? paid?")
                lines.append("g_custom ::= '~' alpha alpha alpha*")
                lines.append(
                    "field_g ::= 'g' ( g_domain | g_custom ) ( '/' ( g_domain | g_custom ) )*"
                )
            elif code == "b":
                aspire_str = " aspire?" if has_aspire else ""
                lines.append(
                    f"field_b ::= 'b' odigit{aspire_str} '/' odigit{aspire_str}"
                )
            elif code == "v":
                lines.append("field_v ::= 'v' odigit '/' odigit")
            else:
                lines.append(
                    f"field_{code} ::= '{code}' ( alpha | digit | '$' | '+' | '/' | '~' )+"
                )

        lines.append("")

    # ── Block format ──
    lines.append("/* === Block format === */")
    lines.append("")
    lines.append(
        "ugi_block ::= block_header newline block_first_line newline "
        "block_field_line+ block_footer"
    )
    lines.append("")
    lines.append("block_header ::= '------- BEGIN UGI BLOCK -------'")
    lines.append("block_footer ::= '-------- END UGI BLOCK --------'")
    lines.append("")
    lines.append(
        "block_first_line ::= 'v:' version ' @' handle ( ' ' block_geek_field )?"
    )
    lines.append("")
    lines.append(
        "block_geek_field ::= 'G' ( g_domain | g_custom ) ( '/' ( g_domain | g_custom ) )*"
    )
    lines.append("")
    lines.append("block_field_line ::= block_field ( ' ' block_field )* newline")
    lines.append("")
    lines.append(
        "block_field ::= alpha ( alpha | digit | '$' | '+' | '/' | '~' )+"
    )
    lines.append("")

    # ── Terminals ──
    lines.append("/* === Terminals === */")
    lines.append("")
    lines.append("alpha ::= [a-zA-Z]")
    lines.append("digit ::= [0-9]")
    lines.append("newline ::= #xD #xA | #xA")
    lines.append("")

    output = "\n".join(lines)

    os.makedirs(os.path.dirname(os.path.abspath(output_path)), exist_ok=True)
    with open(output_path, "w") as f:
        f.write(output)

    print(f"Generated {output_path}")


if __name__ == "__main__":
    main()