scritcher/src/lang.zig

const std = @import("std");

const plugin = @import("plugin.zig");

pub const ParseError = error{
    OutOfMemory,
    ArgRequired,
    ParseFail,
};

pub const CommandType = enum {
    /// "LV2 Commands" are commands that receive split, index, and then receive
    /// any f64 arguments.
    lv2_command,
};

fn LV2Command(
    comptime tag: Command.Tag,
    comptime plugin_url: []const u8,
    comptime LV2Parameters: type,
) type {
    return struct {
        pub const base_tag = tag;
        pub const command_type = CommandType.lv2_command;
        pub const lv2_url = plugin_url;

        base: Command,
        split: usize,
        index: usize,
        parameters: LV2Parameters,
    };
}

pub const Command = struct {
    tag: Tag,

    pub const Tag = enum {
        noop,
        load,
        quicksave,
        runqs,

        amp,
        rflanger,
        eq,
        phaser,
        mbeq,
        chorus,
        pitchscaler,
        reverb,
        highpass,
        delay,
        vinyl,
        revdelay,
        gate,
        detune,
        overdrive,
        degrade,
        repsycho,
        talkbox,
        dyncomp,
        thruzero,
        foverdrive,
        gverb,
        invert,
        tapedelay,
        moddelay,
        multichorus,
        saturator,
        vintagedelay,

        noise,
        wildnoise,
        write,
        embed,

        rotate,
    };

    pub fn tagToType(tag: Tag) type {
        return switch (tag) {
            .noop => Noop,
            .load => Load,
            .quicksave => Quicksave,
            .runqs => RunQS,

            .amp => Amp,
            .rflanger => RFlanger,
            .eq => Eq,
            .phaser => Phaser,
            // .mbeq => Mbeq,
            // .chorus => Chorus,
            // .pitchscaler => Pitchscaler,
            // .reverb => Reverb,
            // .highpass => Highpass,
            // .delay => Delay,
            // .vinyl => Vinyl,
            // .revdelay => Revdelay,
            // .gate => Gate,
            // .detune => Detune,
            // .overdrive => Overdrive,
            // .degrade => Degrade,
            // .repsycho => Repsycho,
            // .talkbox => Talkbox,
            // .dyncomp => Dyncomp,
            // .thruzero => Thruzero,
            // .foverdrive => Foverdrive,
            // .gverb => Gverb,
            // .invert => Invert,
            // .tapedelay => Tapedelay,
            // .moddelay => Moddelay,
            // .multichorus => Multichorus,
            // .saturator => Saturator,
            // .vintagedelay => Vintagedelay,

            else => @panic("TODO"),
        };
    }

    pub fn cast(base: *const @This(), comptime T: type) ?*const T {
        if (base.tag != T.base_tag)
            return null;

        return @fieldParentPtr(T, "base", base);
    }

    pub fn print(base: *const @This()) void {
        std.debug.warn("tag: {}\n", .{base.tag});
    }

    pub const Noop = struct {
        pub const base_tag = Tag.noop;
        base: Command,
    };

    pub const Load = struct {
        pub const base_tag = Tag.load;
        base: Command,
        path: []const u8,
    };

    pub const Quicksave = struct {
        pub const base_tag = Tag.quicksave;
        base: Command,
    };

    pub const RunQS = struct {
        pub const base_tag = Tag.runqs;
        program: []const u8,
        base: Command,
    };

    pub const Amp = LV2Command(
        .amp,
        "http://lv2plug.in/plugins/eg-amp",
        struct {
            gain: f32
        },
    );

    pub const RFlanger = LV2Command(
        .rflanger,
        "http://plugin.org.uk/swh-plugins/retroFlange",
        struct {
            delay_depth_avg: f32, law_freq: f32
        },
    );

    pub const Eq = LV2Command(
        .rflanger,
        "http://plugin.org.uk/swh-plugins/dj_eq_mono",
        struct {
            lo: f32, mid: f32, hi: f32
        },
    );

    pub const Phaser = LV2Command(
        .rflanger,
        "http://plugin.org.uk/swh-plugins/lfoPhaser",
        struct {
            lfo_rate: f32, lfo_depth: f32, fb: f32, spread: f32
        },
    );
};

pub const CommandList = std.ArrayList(*Command);
pub const ArgList = std.ArrayList([]const u8);

pub const KeywordMap = std.StringHashMap(CommandType);

/// A parser.
pub const Lang = struct {
    allocator: *std.mem.Allocator,

    has_error: bool = false,
    line: usize = 0,

    pub fn init(allocator: *std.mem.Allocator) Lang {
        return Lang{
            .allocator = allocator,
        };
    }

    pub fn deinit(self: *Lang) void {}

    pub fn reset(self: *Lang) void {
        self.has_error = false;
        self.line = 0;
    }
    fn doError(self: *Lang, comptime fmt: []const u8, args: var) void {
        std.debug.warn("error at line {}: ", .{self.line});
        std.debug.warn(fmt, args);
        std.debug.warn("\n", .{});
        self.has_error = true;
    }

    fn parseCommandArguments(
        self: *@This(),
        comptime command_struct: type,
        tok_it: *std.mem.TokenIterator,
        commands: *CommandList,
    ) !void {
        // Based on the command struct fields, we can parse the arguments.
        var cmd = try self.allocator.create(command_struct);
        const is_lv2_command = switch (command_struct.base_tag) {
            .noop, .load, .quicksave, .runqs => false,
            else => command_struct.command_type == .lv2_command,
        };

        // TODO: crash when no arguments are left but we still need
        // arguments...

        if (is_lv2_command) {
            cmd.split = try std.fmt.parseInt(usize, tok_it.next().?, 10);
            cmd.index = try std.fmt.parseInt(usize, tok_it.next().?, 10);

            inline for (@typeInfo(@TypeOf(cmd.parameters)).Struct.fields) |cmd_field| {
                const arg = tok_it.next().?;
                const argument_value = switch (cmd_field.field_type) {
                    f32 => try std.fmt.parseFloat(f32, arg),
                    else => @compileError("LV2 parameter struct can only have f32 fields"),
                };

                std.debug.warn("parsing {}, arg of type {} => {}\n", .{
                    @typeName(command_struct),
                    @typeName(@TypeOf(argument_value)),
                    argument_value,
                });

                @field(cmd.parameters, cmd_field.name) = argument_value;
            }
        } else {
            inline for (@typeInfo(command_struct).Struct.fields) |cmd_field| {
                comptime {
                    if (std.mem.eql(u8, cmd_field.name, "base")) {
                        continue;
                    }
                }
                const arg = tok_it.next().?;
                const argument_value = switch (cmd_field.field_type) {
                    usize => try std.fmt.parseInt(usize, arg, 10),
                    i32 => try std.fmt.parseInt(i32, arg, 10),
                    f32 => try std.fmt.parseFloat(f32, arg),
                    []const u8 => try self.allocator.dupe(u8, arg),
                    else => @panic("Invalid parameter type (" ++ @typeName(cmd_field.field_type) ++ ") left on command struct " ++ @typeName(command_struct) ++ "."),
                };

                std.debug.warn("parsing {}, arg of type {} => {}\n", .{
                    @typeName(command_struct),
                    @typeName(@TypeOf(argument_value)),
                    argument_value,
                });

                @field(cmd, cmd_field.name) = argument_value;
            }
        }

        cmd.base.tag = command_struct.base_tag;
        const command = cmd.base.cast(command_struct).?;
        std.debug.warn("cmd: {}\n", .{command});

        try commands.append(&cmd.base);
    }

    pub fn parse(self: *Lang, data: []const u8) !CommandList {
        var splitted_it = std.mem.split(data, ";");
        var cmds = CommandList.init(self.allocator);

        while (splitted_it.next()) |stmt_orig| {
            self.line += 1;
            var stmt = std.mem.trimRight(u8, stmt_orig, "\n");
            stmt = std.mem.trimLeft(u8, stmt, "\n");

            if (stmt.len == 0) continue;
            if (std.mem.startsWith(u8, stmt, "#")) continue;

            // TODO better tokenizer instead of just tokenize(" ")...maybe????
            var tok_it = std.mem.tokenize(stmt, " ");

            var cmd_opt = tok_it.next();
            if (cmd_opt == null) {
                self.doError("No command given", .{});
                continue;
            }
            const command_string = cmd_opt.?;

            var found: bool = false;

            inline for (@typeInfo(Command).Struct.decls) |cmd_struct_decl| {
                switch (cmd_struct_decl.data) {
                    .Type => |typ| switch (@typeInfo(typ)) {
                        .Struct => {},
                        else => continue,
                    },
                    else => continue,
                }

                const struct_name = cmd_struct_decl.name;
                comptime var lowered_command_name = [_]u8{0} ** struct_name.len;
                comptime {
                    for (struct_name) |c, i| {
                        lowered_command_name[i] = std.ascii.toLower(c);
                    }
                }

                // if we have a match, we know the proper struct type
                // to use. this actually works compared to storing command_struct
                // in a variable because then that variable must be comptime.

                // the drawback of this approach is that our emitted code is basically linear
                // because we don't use the hashmap anymore. maybe #5359 can help.

                if (std.mem.eql(u8, &lowered_command_name, command_string)) {
                    found = true;
                    const cmd_struct_type = cmd_struct_decl.data.Type;
                    try self.parseCommandArguments(cmd_struct_type, &tok_it, &cmds);
                }
            }

            if (!found) {
                self.doError("Unknown command '{}' ({})", .{ command_string, command_string.len });
                continue;
            }

            // try cmds.append(cmd);
        }

        if (self.has_error) return ParseError.ParseFail;

        return cmds;
    }
};

test "noop" {
    var lang = Lang.init(std.heap.direct_allocator);
    defer lang.deinit();

    var cmds = try lang.parse("noop;");
    defer cmds.deinit();

    std.testing.expectEqual(cmds.len, 1);
    std.testing.expectEqual(cmds.items[0].command, .Noop);
}

test "load, phaser, quicksave" {
    var lang = Lang.init(std.heap.direct_allocator);
    defer lang.deinit();

    const prog =
        \\load :0;
        \\phaser 3 1 25 0.25 0 1;
        \\quicksave;
    ;

    var cmds = try lang.parse(prog);
    defer cmds.deinit();

    std.testing.expectEqual(cmds.len, 3);
    std.testing.expectEqual(cmds.items[0].command, .Load);
    std.testing.expectEqual(cmds.items[1].command, .Phaser);
    std.testing.expectEqual(cmds.items[2].command, .Quicksave);
}