#!/usr/bin/env python3
import json
import unicodedata
import argparse
import sys

def get_glyph_name(ch):
    """
    Return the official Unicode name of ch, or its codepoint if unnamed.
    """
    try:
        return unicodedata.name(ch)
    except ValueError:
        # Fallback to codepoint string
        return f"U+{ord(ch):04X}"

def format_rust_array(matrix):
    """
    Given a 2D list of ints, return a Rust-style nested array string.
    """
    lines = []
    for row in matrix:
        # join numbers with commas, no spaces after commas to match example
        line = "[" + ",".join(str(v) for v in row) + "],"
        lines.append("        " + line)
    return "\n".join(lines)

def main():
    parser = argparse.ArgumentParser(
        description="Convert JSON glyph bitmaps to a Rust source file."
    )
    parser.add_argument("input_json", help="Path to input JSON file")
    parser.add_argument("output_rs", help="Path to write Rust source file")
    args = parser.parse_args()

    # Load JSON
    with open(args.input_json, "r", encoding="utf-8") as f:
        data = json.load(f)

    if not data:
        print("No glyphs found in JSON.", file=sys.stderr)
        sys.exit(1)

    # Determine dimensions from first glyph
    first_matrix = next(iter(data.values()))
    rows = len(first_matrix)
    cols = len(first_matrix[0]) if rows > 0 else 0

    # Begin emitting Rust code
    with open(args.output_rs, "w", encoding="utf-8") as out:
        out.write("// This file was generated by mkrust.py\n")
        out.write(f"pub const GLYPH_BITMAPS: &[(char, [[u8; {cols}]; {rows}])] = &[\n")

        for ch, matrix in data.items():
            name = get_glyph_name(ch)
            # comment with the Unicode name
            out.write(f"    // {name}\n")
            out.write(f"    ('{ch}', [\n")
            out.write(format_rust_array(matrix) + "\n")
            out.write("    ]),\n\n")

        out.write("];\n")

if __name__ == "__main__":
    main()