// SPDX-FileCopyrightText: 2024 Himbeer <himbeer@disroot.org>
//
// SPDX-License-Identifier: AGPL-3.0-or-later

const std = @import("std");

const Console = @import("Console.zig");
const process = @import("process.zig");
const syscall = @import("syscall.zig");
const sysexchange = @import("sysexchange.zig");
const userinit = @import("userinit.zig");
const vfs = @import("vfs.zig");

const Result = sysexchange.Result;
const io = std.io;
const tar = std.tar;

const File = tar.Iterator(io.FixedBufferStream([]const u8).Reader).File;

const iofs = struct {
    const debug = struct {
        fn write(ptr: [*]const u8, len: usize) callconv(.C) Result(usize) {
            const bytes = ptr[0..len];

            const console = Console.autoChoose() orelse {
                return Result(usize).fromAnyTypeOrError(Error.NoConsole);
            };
            const w = console.writer();

            w.print("{s}", .{bytes}) catch |err| {
                return Result(usize).fromAnyTypeOrError(err);
            };
            return Result(usize).fromAnyTypeOrError(bytes.len);
        }
    };
};

pub const Error = error{
    NoTarFileInitializer,
    NoConsole,
};

pub fn provideBuiltin() !void {
    try addDir("/io");
    try addDir("/userinit");

    try provideConsole();
    try provideUserinit();
}

fn provideConsole() !void {
    try vfs.provideResource("/io/debug", .{
        .tag = .stream,
        .data = .{
            .stream = .{
                .readFn = null,
                .writeFn = iofs.debug.write,
            },
        },
    }, 0);
}

fn provideUserinit() !void {
    var userinit_stream = io.fixedBufferStream(userinit.tarball);
    const reader = userinit_stream.reader();

    var file_name_buffer: [4086]u8 = undefined;
    var link_name_buffer: [4086]u8 = undefined;
    var path_buffer: [4096]u8 = undefined;

    var it = tar.iterator(reader, .{
        .file_name_buffer = file_name_buffer[0..],
        .link_name_buffer = link_name_buffer[0..],
    });

    while (try it.next()) |file| {
        const path = try std.fmt.bufPrint(path_buffer[0..], "/userinit/{s}", .{file.name});
        switch (file.kind) {
            .file => try addFile(path, file),
            .directory => try addDir(path),
            .sym_link => {},
        }
    }
}

fn addFile(path: []const u8, file: File) !void {
    const allocator = vfs.treeRoot().allocator;

    const initializer = try allocator.create(File);
    initializer.* = file;

    try vfs.provideResource(path, .{
        .tag = .file,
        .data = .{
            .file = .{
                .openFn = open,
                .readFn = read,
                .writeFn = null,
                .closeFn = close,
                .initializer = initializer,
            },
        },
    }, 0);
}

fn addDir(path: []const u8) !void {
    const allocator = vfs.treeRoot().allocator;
    const tree = try allocator.create(vfs.Tree);
    tree.* = vfs.Tree.init(allocator);

    try vfs.provideResource(path, .{
        .tag = .dir,
        .data = .{ .dir = tree },
    }, 0);
}

fn open(initializer: ?*anyopaque, _: u16) callconv(.C) Result(*anyopaque) {
    const file_template: *File = @alignCast(@ptrCast(initializer orelse {
        return Result(*anyopaque).fromAnyTypeOrError(Error.NoTarFileInitializer);
    }));

    const allocator = vfs.treeRoot().allocator;
    const context = allocator.create(File) catch |err| {
        return Result(*anyopaque).fromAnyTypeOrError(err);
    };
    context.* = file_template.*;

    return Result(*anyopaque).fromAnyTypeOrError(context);
}

fn read(context: *anyopaque, ptr: [*]u8, len: usize) callconv(.C) Result(usize) {
    const ctx: *File = @alignCast(@ptrCast(context));

    const buffer = ptr[0..len];
    return Result(usize).fromAnyTypeOrError(ctx.read(buffer));
}

fn close(context: *anyopaque) callconv(.C) void {
    const ctx: *File = @alignCast(@ptrCast(context));

    const allocator = vfs.treeRoot().allocator;
    allocator.destroy(ctx);
}