const std = @import("std");
const assert = std.debug.assert;

const Walk = @import("Walk");
const Decl = Walk.Decl;
const html_render = @import("html_render");

const gpa = std.heap.wasm_allocator;
const log = std.log;

const js = struct {
    extern "js" fn log(ptr: [*]const u8, len: usize) void;
    extern "js" fn panic(ptr: [*]const u8, len: usize) noreturn;
};

pub const std_options: std.Options = .{
    .logFn = logFn,
};

pub fn panic(msg: []const u8, st: ?*std.builtin.StackTrace, addr: ?usize) noreturn {
    _ = st;
    _ = addr;
    log.err("panic: {s}", .{msg});
    @trap();
}

fn logFn(
    comptime message_level: log.Level,
    comptime scope: @TypeOf(.enum_literal),
    comptime format: []const u8,
    args: anytype,
) void {
    const level_txt = comptime message_level.asText();
    const prefix2 = if (scope == .default) ": " else "(" ++ @tagName(scope) ++ "): ";
    var buf: [500]u8 = undefined;
    const line = std.fmt.bufPrint(&buf, level_txt ++ prefix2 ++ format, args) catch l: {
        buf[buf.len - 3 ..][0..3].* = "...".*;
        break :l &buf;
    };
    js.log(line.ptr, line.len);
}

export fn alloc(n: usize) [*]u8 {
    const slice = gpa.alloc(u8, n) catch @panic("OOM");
    return slice.ptr;
}

export fn unpack(tar_ptr: [*]u8, tar_len: usize) void {
    const tar_bytes = tar_ptr[0..tar_len];
    log.debug("received {d} bytes of tar file", .{tar_bytes.len});

    unpackInner(tar_bytes) catch |err| {
        fatal("unable to unpack tar: {s}", .{@errorName(err)});
    };
}

/// Set by `set_input_string`.
var input_string: std.ArrayListUnmanaged(u8) = .{};
var string_result: std.ArrayListUnmanaged(u8) = .{};

export fn set_input_string(len: usize) [*]u8 {
    input_string.resize(gpa, len) catch @panic("OOM");
    return input_string.items.ptr;
}

/// Looks up the root struct decl corresponding to a file by path.
/// Uses `input_string`.
export fn find_file_root() Decl.Index {
    const file: Walk.File.Index = @enumFromInt(Walk.files.getIndex(input_string.items) orelse return .none);
    return file.findRootDecl();
}

export fn decl_source_html(decl_index: Decl.Index) String {
    const decl = decl_index.get();

    string_result.clearRetainingCapacity();
    html_render.fileSourceHtml(decl.file, &string_result, decl.ast_node, .{}) catch |err| {
        fatal("unable to render source: {s}", .{@errorName(err)});
    };
    return String.init(string_result.items);
}

const String = Slice(u8);

fn Slice(T: type) type {
    return packed struct(u64) {
        ptr: u32,
        len: u32,

        fn init(s: []const T) @This() {
            return .{
                .ptr = @intFromPtr(s.ptr),
                .len = s.len,
            };
        }
    };
}

fn unpackInner(tar_bytes: []u8) !void {
    var fbs = std.io.fixedBufferStream(tar_bytes);
    var file_name_buffer: [1024]u8 = undefined;
    var link_name_buffer: [1024]u8 = undefined;
    var it = std.tar.iterator(fbs.reader(), .{
        .file_name_buffer = &file_name_buffer,
        .link_name_buffer = &link_name_buffer,
    });
    while (try it.next()) |tar_file| {
        switch (tar_file.kind) {
            .file => {
                if (tar_file.size == 0 and tar_file.name.len == 0) break;
                if (std.mem.endsWith(u8, tar_file.name, ".zig")) {
                    log.debug("found file: '{s}'", .{tar_file.name});
                    const file_name = try gpa.dupe(u8, tar_file.name);
                    if (std.mem.indexOfScalar(u8, file_name, '/')) |pkg_name_end| {
                        const pkg_name = file_name[0..pkg_name_end];
                        const gop = try Walk.modules.getOrPut(gpa, pkg_name);
                        const file: Walk.File.Index = @enumFromInt(Walk.files.entries.len);
                        if (!gop.found_existing or
                            std.mem.eql(u8, file_name[pkg_name_end..], "/root.zig") or
                            std.mem.eql(u8, file_name[pkg_name_end + 1 .. file_name.len - ".zig".len], pkg_name))
                        {
                            gop.value_ptr.* = file;
                        }
                        const file_bytes = tar_bytes[fbs.pos..][0..@intCast(tar_file.size)];
                        assert(file == try Walk.add_file(file_name, file_bytes));
                    }
                } else {
                    log.warn("skipping: '{s}' - the tar creation should have done that", .{tar_file.name});
                }
            },
            else => continue,
        }
    }
}

fn fatal(comptime format: []const u8, args: anytype) noreturn {
    var buf: [500]u8 = undefined;
    const line = std.fmt.bufPrint(&buf, format, args) catch l: {
        buf[buf.len - 3 ..][0..3].* = "...".*;
        break :l &buf;
    };
    js.panic(line.ptr, line.len);
}