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// Copyright 2025 Shota FUJI
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0

const std = @import("std");

const ApiSpec = @import("./ApiSpec.zig");

fn writeBaseType(writer: anytype, t: ApiSpec.CBaseType) !void {
    switch (t) {
        .bool, .char, .float, .double, .void => try writer.writeAll(@tagName(t)),
        .custom => |name| try writer.writeAll(name),
        .string => try writer.writeAll("const char *"),
        .int, .uint => |bits| {
            try std.fmt.format(writer, "{s}{d}_t", .{
                if (t == .int) "int" else "uint",
                bits,
            });
        },
    }
}

fn writeType(writer: anytype, t: ApiSpec.CType) !void {
    switch (t) {
        .pointer => |pointer| {
            if (pointer.@"const") {
                try writer.writeAll("const ");
            }

            try writeBaseType(writer, pointer.type);
            try writer.writeAll(" *");
        },
        .value => |child| try writeBaseType(writer, child),
    }
}

fn writeFunction(writer: anytype, cname: []const u8, f: ApiSpec.Function) !void {
    try writeType(writer, f.return_type);
    try std.fmt.format(writer, " {s}_{s}(", .{ cname, f.name });

    for (f.parameters, 0..) |param, i| {
        if (i > 0) {
            try writer.writeAll(", ");
        }

        try writeType(writer, param.type);
    }
    try writer.writeAll(");\n");
}

pub fn main() !void {
    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
    defer arena.deinit();

    const allocator = arena.allocator();

    var args = std.process.ArgIterator.init();
    defer args.deinit();

    _ = args.skip();

    const input = args.next() orelse {
        return error.NoInputFile;
    };

    const output = args.next() orelse {
        return error.NoOutputFile;
    };

    if (args.next()) |_| {
        return error.TooManyArgument;
    }

    const input_file = try std.fs.cwd().openFile(input, .{});
    defer input_file.close();

    var source = std.json.reader(allocator, input_file.reader());

    const parsed = try std.json.parseFromTokenSource(ApiSpec, allocator, &source, .{});
    defer parsed.deinit();

    const spec = parsed.value;

    const output_file = try std.fs.cwd().createFile(output, .{});
    defer output_file.close();

    const writer = output_file.writer();

    try writer.writeAll(
        \\#ifndef ROON_MSG_H
        \\#define ROON_MSG_H
        \\
        \\#include <stdbool.h>
        \\#include <stddef.h>
        \\#include <stdint.h>
        \\
        \\
    );

    for (spec.items) |item| {
        switch (item) {
            .@"enum" => |info| {
                try writer.writeAll("typedef enum {\n");

                const ns = try std.ascii.allocUpperString(allocator, info.cname);

                for (info.fields) |field| {
                    try std.fmt.format(writer, "\t{s}_{s} = {d},\n", .{
                        ns, try std.ascii.allocUpperString(allocator, field.name), field.value,
                    });
                }

                try std.fmt.format(writer, "}} {s};\n\n", .{info.cname});
            },
            .@"opaque" => |info| {
                try std.fmt.format(writer, "typedef void {s};\n", .{info.cname});

                try writeFunction(writer, info.cname, info.new_function);

                for (info.member_functions) |member_fn| {
                    try writeFunction(writer, info.cname, member_fn);
                }

                try writer.writeByte('\n');
            },
            .@"struct" => |info| {
                try writer.writeAll("typedef struct {\n");
                // Zig has compiler bug that prevents using tab inside multiline string.
                try writer.writeAll("\tsize_t __rc;\n");

                for (info.fields) |field| {
                    try writer.writeByte('\t');
                    try writeType(writer, field.type);
                    if (field.type == .pointer and
                        std.mem.endsWith(u8, field.name, "_ptr") and
                        field.type.pointer.type == .custom)
                    {
                        try writer.writeByte('*');
                    }
                    try writer.writeByte(' ');
                    try std.fmt.format(writer, "{s};\n", .{field.name});
                }
                try std.fmt.format(writer, "}} {s};\n", .{info.cname});

                if (info.new_function) |f| {
                    try writeFunction(writer, info.cname, f);
                }

                for (info.member_functions) |f| {
                    try writeFunction(writer, info.cname, f);
                }

                try writer.writeByte('\n');
            },
        }
    }

    try writer.writeAll("#endif\n");
}