PLoop-Switcher

siwtch.lua

require "PLoop" (function(_ENV)
    __Sealed__()
    struct "Case" (function(_ENV)
        import "System.Text"

        export { unpack = unpack or table.unpack }

        member "vars"       { type = Variables, require = true }
        member "func"       { type = Callable, require = true }

        -- Auto gen
        member "min"        { type = Number }
        member "max"        { type = Number }
        member "validate" { type = Function }
        member "process"    { type = Function }

        _ValTemplate        = TemplateString[[
            return function(
                    @for i = 1, count do
                        var@i @(i < count and "," or "")
                    @end
                )
                return function(
                        @for i = 1, count do
                            arg@i @(i < count and "," or "")
                        @end
                    )
                    local ret, msg
                    @for i = 1, count do
                        local var = var@i
                        if arg@i ~= null then
                            ret, msg = var.validate(var.type, arg@i, true)
                            if msg then return false end
                        elseif not var.optional then
                            return false
                        end
                    @end
                    return true
                end
            end
        ]]

        _ValVargsTemplate   = TemplateString[[
            return function(
                    @for i = 1, count do
                        var@i @(i < count and "," or "")
                    @end
                )
                return function(
                        @for i = 1, count - 1 do
                            arg@i,
                        @end
                        ...
                    )
                    local ret, msg
                    @for i = 1, count - 1 do
                        local var = var@i
                        if arg@i ~= null then
                            ret, msg = var.validate(var.type, arg@i, true)
                            if msg then return false end
                        elseif not var.optional then
                            return false
                        end
                    @end

                    local var = var@count
                    for i = 1, select("#", ...) do
                        local val = select(i, ...)
                        if val ~= null then
                            ret, msg = var.validate(var.type, val, true)
                            if msg then return false end
                        elseif i < var.mincount then
                            return false
                        end
                    end
                    return true
                end
            end
        ]]

        _PassTemplate           = TemplateString[[
            return function(
                    @for i = 1, count do
                        var@i @(i < count and "," or "")
                    @end
                )
                return function(
                        @for i = 1, count do
                            arg@i @(i < count and "," or "")
                        @end
                    )
                    @for i = 1, count do
                        local var = var@i
                        if arg@i ~= null then
                            if not var.immutable then
                                arg@i = var.validate(var.type, arg@i)
                            end
                        else
                            arg@i = var.default
                        end
                    @end
                    return
                    @for i = 1, count do
                        arg@i @(i < count and "," or "")
                    @end
                end
            end
        ]]

        _PassVargsTemplate      = TemplateString[[
            return function(
                    @for i = 1, count do
                        var@i @(i < count and "," or "")
                    @end
                )
                return function(
                        @for i = 1, count - 1 do
                            arg@i,
                        @end
                        ...
                    )
                    @for i = 1, count - 1 do
                        local var = var@i
                        if arg@i ~= null then
                            if not var.immutable then
                                arg@i = var.validate(var.type, arg@i)
                            end
                        else
                            arg@i = var.default
                        end
                    @end

                    local var = var@count
                    if var.immutable then
                        return
                        @for i = 1, count - 1 do
                            arg@i,
                        @end
                        ...
                    else
                        local rets = { ... }
                        for i, v in ipairs(rets) do
                            if v ~= null then
                                v = var.validate(var.type, v)
                            end
                            rets[i] = v
                        end
                        return
                        @for i = 1, count - 1 do
                            arg@i,
                        @end
                        unpack(rets)
                    end
                end
            end
        ]]

        _AutoValidGen       = setmetatable( { [0] = function() return true end }, {
            __index         = function(self, count)
                local func  = Toolset.loadsnippet(_ValTemplate{ count = count }, "Case_Val_" .. count, _ENV)()
                rawset(self, count, func)
                return func
            end
        })

        _AutoValidVargGen   = setmetatable({}, {
            __index         = function(self, count)
                local func  = Toolset.loadsnippet(_ValVargsTemplate{ count = count }, "Case_VargsVal_" .. count, _ENV)()
                rawset(self, count, func)
                return func
            end
        })

        _AutoPassGen        = setmetatable( { [0] = function() return end }, {
            __index         = function(self, count)
                local func  = Toolset.loadsnippet(_PassTemplate{ count = count }, "Case_Pass_" .. count, _ENV)()
                rawset(self, count, func)
                return func
            end
        })

        _AutoPassVargGen    = setmetatable({}, {
            __index         = function(self, count)
                local func  = Toolset.loadsnippet(_PassVargsTemplate{ count = count }, "Case_VargsPass_" .. count, _ENV)()
                rawset(self, count, func)
                return func
            end
        })

        function __init(self)
            local len       = #self.vars
            local min
            local max       = len
            local immutable = true
            local isvaragrs = false

            for i = 1, len do
                local var   = self.vars[i]

                if var.optional then
                    min     = min or i - 1
                end

                if var.varargs then
                    isvargs = true
                    max     = 255

                    if not var.mincount or var.mincount == 0 then
                        min = min or i - 1
                    else
                        min = i + var.mincount - 1
                    end
                end

                if not var.immutable then immutable = false end
            end

            self.min        = min or len
            self.max        = max

            self.validate = (isvaragrs and _AutoValidVargGen or _AutoValidGen)[len](unpack(self.vars))

            if immutable then
                self.process= self.func
            else
                local pass  = (isvaragrs and _AutoPassVargGen or _AutoPassGen)[len](unpack(self.vars))
                local func  = self.func
                self.process= function(...) return func(pass(...)) end
            end
        end
    end)

    __Sealed__()
    class "Switch" (function(_ENV)
        __Arguments__{ Case * 1 }
        function __new(cls, ...)
            return { ... }, true
        end

        function __ctor(self)
            local count     = #self

        end

        function __call(self, ...)
            local count     = select("#", ...)

            for i = 1, #self do
                local case  = self[i]

                if case.min <= count and count <= case.max then
                    if case.validate(...) then
                        return case.process(...)
                    end
                end
            end
        end
    end)


    switcher = Switch(
        Case (
            { Number/0 },
            function (num) print("Age", num) end
        ),
        Case (
            { String },
            "x => print('Name', x)"
        )
    )

    switcher(3)
    switcher("Ann")
    switcher()
end)