exceptional

local function getErrorData(errString)
    local all, chunk, line, text = errString:match("^((.+):(%d+):%s(.+))$")
    local exceptional, excepDetails = text:match("^(%[Exceptional%:(.+)%])$")
    if all ~= nil and exceptional == nil then
        --# It's a regular Lua error.
        local details = {
            ["Type"] = "LuaError",
            ["Message"] = text,
            ["Line"] = tonumber(line),
            ["Chunk"] = chunk,
            ["Plain"] = errString
        }
        return details
    elseif all ~= nil and exceptional ~= nil then
        --# It's an exception.
        local details = textutils.unserialise(excepDetails)
        details.Plain = errString
        details.Line = tonumber(line)
        details.Chunk = chunk
        return details
    else
        --# Don't know how to handle it...
        local details = {
            ["Type"] = "Unknown",
            ["Line"] = tonumber(line),
            ["Chunk"] = chunk,
            ["Plain"] = errString
        }
    end
end

local function makeCatch(reqType, tbl, errData)
    return function(self, catchFunc)
        if (type(self) == "function" or type(self) == "table") and catchFunc == nil then
            catchFunc = self
        end

        if type(catchFunc) == "table" then
            for _,v in pairs(catchFunc) do
                if type(v) == "function" then
                    catchFunc = v
                    break
                end
            end
        end

        if type(catchFunc) ~= "function" then
            error("catch argument couldn't be resolved to a function!", 2)
            return
        end

        if reqType == nil or errData.Type == reqType then
            catchFunc(errData)
        end
        return tbl
    end
end

local env = getfenv(0)
env["try"] = function(f)
    if f == nil then
        error("throw argument couldn't be resolved to a function!", 2)
    end

    local firstErr = nil

    if type(f) == "function" then
        local ok, err = pcall(f)
        if not ok then
            firstErr = err
        end
    elseif type(f) == "table" then
        for _,v in pairs(f) do
            local ok, err = pcall(v)
            if not ok then
                firstErr = err
                break
            end
        end
    end

    local handled = {}

    if firstErr ~= nil then
        --# There was an error!
        return setmetatable({}, {
            __index = function(t, k)
                if k == "catch" then
                    k = nil
                end

                if k ~= nil then
                    handled[k] = true
                end

                local errData = getErrorData(firstErr)
                if k == nil and handled[errData.Type] then
                    return function() return t end
                end
                return makeCatch(k, t, errData)
            end,

            __newindex = function() end
        })
    else
        --# Don't care...
        return setmetatable({}, {
            __index = function(t, k)
                return function()
                    return t
                end
            end
        })
    end
end

env["throw"] = function(msg)
    if type(msg) == "string" then
        error(msg, 2)
    elseif type(msg) == "table" then
        if msg.Type == nil then
            error("throw table has no type!", 2)
        end
        error("[Exceptional:" .. textutils.serialise(msg) .. "]", 2)
    end
end