windowsCreateProcessSupportsExtension

fn windowsCreateProcessSupportsExtension(ext: []const u16) ?process.WindowsExtension {
    comptime {
        // Ensures keeping this function in sync with the enum.
        const field_names = @typeInfo(process.WindowsExtension).@"enum".field_names;
        assert(field_names.len == 4);
        assert(@backingInt(process.WindowsExtension.bat) == 0);
        assert(@backingInt(process.WindowsExtension.cmd) == 1);
        assert(@backingInt(process.WindowsExtension.com) == 2);
        assert(@backingInt(process.WindowsExtension.exe) == 3);
    }

    if (ext.len != 4) return null;
    const State = enum {
        start,
        dot,
        b,
        ba,
        c,
        cm,
        co,
        e,
        ex,
    };
    var state: State = .start;
    for (ext) |c| switch (state) {
        .start => switch (c) {
            '.' => state = .dot,
            else => return null,
        },
        .dot => switch (c) {
            'b', 'B' => state = .b,
            'c', 'C' => state = .c,
            'e', 'E' => state = .e,
            else => return null,
        },
        .b => switch (c) {
            'a', 'A' => state = .ba,
            else => return null,
        },
        .c => switch (c) {
            'm', 'M' => state = .cm,
            'o', 'O' => state = .co,
            else => return null,
        },
        .e => switch (c) {
            'x', 'X' => state = .ex,
            else => return null,
        },
        .ba => switch (c) {
            't', 'T' => return .bat,
            else => return null,
        },
        .cm => switch (c) {
            'd', 'D' => return .cmd,
            else => return null,
        },
        .co => switch (c) {
            'm', 'M' => return .com,
            else => return null,
        },
        .ex => switch (c) {
            'e', 'E' => return .exe,
            else => return null,
        },
    };
    return null;
}