abstract type 特殊结构 end
mutable struct 文件
    par::Union{特殊结构,Nothing}
    name::String
    content::String
end
mutable struct 目录 <: 特殊结构
    par::Union{目录,Nothing}
    name::String
    files::Dict{String,文件}
    dirs::Dict{String,目录}
end
目录(par::Union{目录,Nothing}, name::String) = 目录(par, name, Dict{String,文件}(), Dict{String,目录}())
mutable struct 文件系统
    root::目录
    current::目录
end
function 文件系统()
    rt = 目录(nothing, "")
    cu = rt
    return 文件系统(rt, cu)
end

function getpath(dir::目录; full::Bool=false, relative::目录=dir)
    if full
        s = dir.name
		isnothing(dir.par) && return "/"
        t = dir
        while true
            t = t.par
			isnothing(t.par) && return "/$s"
            s = "$(t.name)/$s"
        end
    else
        s = dir.name
        t = dir
        while true
            t = t.par
            if t === nothing
                return "/$s"
            elseif t == relative
                return s
            end
            s = "$(t.name)/$s"
        end
    end
end
function getdir(dir::目录, path::Vector{T}) where {T<:AbstractString}
    res = dir
    for i in path
        if i == ".."
            if res !== nothing
                res = res.par
            end
        elseif i != "."
            if haskey(res.dirs, i)
                res = @inbounds res.dirs[i]
            else
                throw("未在$(getpath(res))找到下一级目录")
            end
        end
    end
    return res
end
function getdir(fs::文件系统, path::AbstractString)
    v = splitpath(path)
    if isempty(v)
        throw("路径不能为空")
    end
    d = fs.current
    if v[1] == "/"
        d = fs.root
        popfirst!(v)
    end
    return getdir(d, v)
end
function getpardir(fs::文件系统, path::AbstractString)::Pair
    v = splitpath(path)
    if isempty(v)
        throw("路径不能为空")
    end
    d = fs.current
    if v[1] == "/"
        d = fs.root
        popfirst!(v)
        if isempty(v)
            throw("路径不能为空")
        end
    end
    last = pop!(v)
    return Pair(getdir(d, v), last)
end
function getfile(fs::文件系统, path::AbstractString)
    v = splitpath(path)
    if isempty(v)
        throw("路径不能为空")
    end
    fname = pop!(v)
    d = fs.current
    if v[1] == "/"
        d = fs.root
        popfirst!(v)
    end
    dir = getdir(d, v)
    if haskey(dir.files, fname)
        return @inbounds dir.files[fname]
    else
        throw("未找到该文件")
    end
end

_pwd(fs::文件系统) = getpath(fs.current; full=true)
function _ls(fs::文件系统, target::目录=fs.current)
    for i in target.dirs
        println(i.first, "/")
    end
    for i in target.files
        println(i.first)
    end
end
function _cd(fs::文件系统, path::AbstractString)
    fs.current = getdir(fs, path)
end
function _mkdir(fs::文件系统, path::AbstractString; force::Bool=false)
    pair = getpardir(fs, path)
    dir = pair.first
    name = pair.second
    if force
        dir.dirs[name] = 目录(dir, name)
        return
    end
    if haskey(dir.dirs, name)
        throw("同名目录已存在")
    elseif haskey(dir.files, name)
        throw("同名文件已存在")
    else
        dir.dirs[name] = 目录(dir, name)
    end
end
function _rmdir(fs::文件系统, path::AbstractString)
    pair = getpardir(fs, path)
    dir = pair.first
    name = pair.second
    q = fs.current
    while q !== nothing
        if q == dir
            throw("删除的目录不能包含当前目录")
        end
        q = q.par
    end
    delete!(dir.dirs, name)
end
function _rm(fs::文件系统, path::AbstractString)
    (dir, name) = getpardir(fs, path)
    if haskey(dir.dirs, name)
        delete!(dir.dirs, name)
    elseif haskey(dir.files, name)
        delete!(dir.files, name)
    else
        throw("未找到该资源")
    end
end
function _cp(fs::文件系统, from::AbstractString, to::AbstractString; force::Bool=false)
    (dir, name) = getpardir(fs, from)
    if haskey(dir.dirs, name)
        dirto = getdir(fs, to)
        ori = @inbounds(dir.dirs[name])
        if !force
            haskey(dirto.dirs, name) ? throw("同名目录已存在") :
            haskey(dirto.files, name) ? throw("同名文件已存在") : nothing
        end
        dirto.dirs[name] = 目录(dirto, name, deepcopy(ori.files), deepcopy(ori.dirs))
    elseif haskey(dir.files, name)
        dirto = getdir(fs, to)
        content = @inbounds(dir.files[name].content)
        if !force
            haskey(dirto.dirs, name) ? throw("同名目录已存在") :
            haskey(dirto.files, name) ? throw("同名文件已存在") : nothing
        end
        dirto.files[name] = 文件(dirto, deepcopy(name), deepcopy(content))
    else
        throw("未找到该资源")
    end
end
function _mv(fs::文件系统, from::AbstractString, to::AbstractString; force::Bool=false)
    (dir, name) = getpardir(fs, from)
    if haskey(dir.dirs, name)
        dirto = getdir(fs, to)
        ori = @inbounds(dir.dirs[name])
        if !force
            haskey(dirto.dirs, name) ? throw("同名目录已存在") :
            haskey(dirto.files, name) ? throw("同名文件已存在") : nothing
        end
        dirto.dirs[name] = 目录(dirto, name, ori.files, ori.dirs)
        delete!(dir.dirs, name)
    elseif haskey(dir.files, name)
        dirto = getdir(fs, to)
        content = @inbounds(dir.files[name].content)
        if !force
            haskey(dirto.dirs, name) ? throw("同名目录已存在") :
            haskey(dirto.files, name) ? throw("同名文件已存在") : nothing
        end
        dirto.files[name] = 文件(dirto, name, content)
        delete!(dir.files, name)
    else
        throw("未找到该资源")
    end
end
const simdata = Dict{String,Tuple{UnitRange,UInt8,Symbol}}(
    # "sim"=>(1:1,0x7,"")
    "pwd" => (0:0, 0x5, :pwd),
    "chdir" => (0:0, 0x2, :pwd),
    "ls" => (0:1, 0x1, :ls),
    "dir" => (0:1, 0x2, :ls),
    "readdir" => (0:1, 0x4, :ls),
    "cd" => (1:1, 0x7, :cd),
    "mkdir" => (1:1, 0x7, :mkdir),
    "md" => (1:1, 0x2, :mkdir),
    "rmdir" => (1:1, 0x3, :rmdir),
    "rm" => (1:1, 0x5, :rm),
    "del" => (1:1, 0x2, :rm),
    "cp" => (2:2, 0x5, :cp),
    "copy" => (2:2, 0x2, :cp),
    "mv" => (2:2, 0x7, :mv),
)
function init()
    fs = 文件系统()
    _mkdir(fs, "home")
    _cd(fs, "home")
    fs.current.files["hello.txt"] = 文件(fs.current, "hello.txt", "你好")
    sim = 0x0
    while true
        print("vfs> ")
        s = readline()
        try
            v = split(s)
            if isempty(v)
                continue
            end
            com = ""
            if v[1] == "sim"
                sim = v[2] == "unix" ? 0x0 :
                      v[2] == "windows" ? 0x1 :
                      v[2] == "julia" ? 0x2 :
                      printstyled("不支持的模拟对象"; color=:light_yellow)
                println()
                continue
            elseif v[1] == "quit"
                return
            else
                name = String(v[1])
                if !haskey(simdata, name)
                    throw("不支持的命令")
                end
                data = @inbounds simdata[name]
                vl = length(v) - 1
                if !in(vl, data[1])
                    throw("错误的参数个数")
                end
                if data[2] >> sim & 0x1 != 0x1
                    throw("该环境不支持该命令")
                end
                com = data[3]
            end
            com == :pwd ? println(_pwd(fs)) :
            com == :ls ? _ls(fs, vl == 1 ? getdir(fs, v[2]) : fs.current) :
            com == :cd ? _cd(fs, v[2]) :
            com == :mkdir ? _mkdir(fs, v[2]) :
            com == :rmdir ? _rmdir(fs, v[2]) :
            com == :rm ? _rm(fs, v[2]) :
            com == :cp ? _cp(fs, v[2], v[3]) :
            com == :mv ? _mv(fs, v[2], v[3]) :
            throw("程序出错")
        catch er
            if isa(er, String)
                printstyled(er; color=:light_red)
                println()
            else
                throw(er)
            end
        end
        println()
    end
end

println("""
当前只支持命令格式，不支持额外参数
使用 "sim 目标" 切换模拟环境
""")