DSL for Create train schedules

create-scheduler.lua

--[[
Train schedule DSL by JackMacWindows

Example:

cyclic
to "Station 1" {
  wait 5m, powered
  time = 14:00 daily
}

Can also be represented like this:

cyclic to "Station 1" { wait 5m powered; time = 14 24h }

CC0 license
]]

local function lex(str)
    local state = 0
    local partial = ""
    local tokens = {}
    for c in str:gmatch "." do
        if state == 0 then -- whitespace
            if c:match "[%a_]" then
                partial = c
                state = 1
            elseif c:match "%d" then
                partial = c
                state = 2
            elseif c:match "[<=>{},;]" then
                tokens[#tokens+1] = {type = "symbol", text = c}
            elseif c == '"' then
                state = 3
            elseif c == '\n' then
                tokens[#tokens+1] = {type = "newline", text = "\n"}
            elseif not c:match "%s" then
                error("unexpected '" .. c .. "'", 0)
            end
        elseif state == 1 then -- token
            if c:match "[%w_]" then
                partial = partial .. c
            elseif c:match "%s" then
                tokens[#tokens+1] = {type = "token", text = partial}
                if c == "\n" then tokens[#tokens+1] = {type = "newline", text = "\n"} end
                partial = ""
                state = 0
            elseif c:match "[<=>{},;]" then
                tokens[#tokens+1] = {type = "token", text = partial}
                tokens[#tokens+1] = {type = "symbol", text = c}
                state = 0
            else error("unexpected '" .. c .. "'", 0) end
        elseif state == 2 then -- number
            if c:match "%d" then
                partial = partial .. c
            elseif (c == ":" or c == ".") and not partial:find(c) then
                partial = partial .. c
            elseif c:match "%a" then
                tokens[#tokens+1] = {type = "number", text = partial, unit = c}
                state = 4
            elseif c:match "[<=>{},;]" then
                tokens[#tokens+1] = {type = "number", text = partial}
                tokens[#tokens+1] = {type = "symbol", text = c}
            elseif c:match "%s" then
                tokens[#tokens+1] = {type = "number", text = partial}
                if c == "\n" then tokens[#tokens+1] = {type = "newline", text = "\n"} end
                state = 0
            else error("unexpected '" .. c .. "'", 0) end
        elseif state == 3 then -- quote
            if c == '\\' then
                state = 5
            elseif c == '"' then
                tokens[#tokens+1] = {type = "string", text = partial}
                state = 0
            else partial = partial .. c end
        elseif state == 4 then -- number end (must be whitespace)
            if not c:match "%s" then error("unexpected '" .. c .. "'", 0) end
            if c == "\n" then tokens[#tokens+1] = {type = "newline", text = "\n"}
            elseif c:match "[<=>{},;]" then tokens[#tokens+1] = {type = "symbol", text = c} end
            state = 0
        elseif state == 5 then -- quote escape
            if c == "n" then partial = partial .. "\n"
            elseif c == "t" then partial = partial .. "\t"
            else partial = partial .. c end
            state = 3
        end
    end
    if state == 1 then tokens[#tokens+1] = {type = "token", text = partial}
    elseif state == 2 then tokens[#tokens+1] = {type = "number", text = partial}
    elseif state == 3 or state == 5 then error("unfinished string at eof", 0) end
    return tokens
end

local conditions = {}

local delay_units = {["t"] = 0, ["s"] = 1, ["m"] = 2}
function conditions.wait(next)
    local time = next(false, "number")
    time.unit = time.unit or "s"
    return {
        id = "create:delay",
        data = {
            value = assert(tonumber(time.text), "invalid number near " .. time.text),
            time_unit = assert(time.unit, "invalid unit near " .. time.text .. time.unit)
        }
    }
end

local time_rotations = {["24h"] = 0, ["12h"] = 1, ["6h"] = 2, ["4h"] = 3, ["3h"] = 4, ["2h"] = 5, ["1h"] = 6, ["45m"] = 7, ["30m"] = 8, ["15m"] = 9}
function conditions.time(next)
    local eq = next()
    if eq.type ~= "symbol" or eq.text ~= "=" then error("expected = near " .. eq.text, 0) end
    local time = next(false, "number")
    local hour, min
    if time.text:find ":" then hour, min = time.text:match "([^:]*):(.*)"
    else hour, min = time.text, 0 end
    hour, min = assert(tonumber(hour), "invalid hour"), assert(tonumber(min), "invalid minute")
    if hour < 0 or hour > 23 then error("invalid hour", 0) end
    if min < 0 or min > 59 then error("invalid minute", 0) end
    local rot = next()
    local rotn
    if rot.type == "token" and rot.text == "daily" then rotn = 0
    elseif rot.type == "token" and rot.text == "hourly" then rotn = 6
    else
        assert(rot.type == "number" and rot.unit, "invalid rotation value near " .. rot.text)
        rotn = assert(time_rotations[rot.text .. rot.unit], "invalid rotation value near " .. rot.text .. rot.unit)
    end
    return {
        id = "create:time_of_day",
        data = {
            hour = hour,
            minute = min,
            rotation = rotn
        }
    }
end

local compare_ops = {[">"] = 0, ["<"] = 1, ["="] = 2}
function conditions.fluid(next)
    local name = next(false, "string")
    local op = next(false, "symbol")
    local threshold = next(false, "number")
    local thresholdn = assert(tonumber(threshold.text), "invalid number near " .. threshold.text)
    threshold.unit = threshold.unit or "b"
    if threshold.unit ~= "b" then error("invalid unit near " .. threshold.text .. threshold.unit) end
    return {
        id = "create:fluid_threshold",
        data = {
            bucket = {
                id = name.text,
                count = 1
            },
            threshold = thresholdn,
            operator = assert(compare_ops[op.text], "invalid comparison operator near " .. op.text),
            measure = 0
        }
    }
end

local item_measures = {["i"] = 0, ["s"] = 1}
function conditions.item(next)
    local name = next(false, "string")
    local op = next(false, "symbol")
    local threshold = next(false, "number")
    local thresholdn = assert(tonumber(threshold.text), "invalid number near " .. threshold.text)
    threshold.unit = threshold.unit or "i"
    return {
        id = "create:item_threshold",
        data = {
            item = {
                id = name.text,
                count = 1
            },
            threshold = thresholdn,
            operator = assert(compare_ops[op.text], "invalid comparison operator near " .. op.text),
            measure = assert(item_measures[threshold.unit], "invalid unit near " .. threshold.text .. threshold.unit)
        }
    }
end

function conditions.players(next)
    local op = next(false, "symbol")
    if op.text ~= ">" and op.text ~= "=" then error("invalid comparison operator near " .. op.text, 0) end
    local count = next(false, "number")
    local n = assert(tonumber(count.text), "invalid number near " .. count.text)
    if n < 0 then error("invalid player count near " .. n, 0) end
    return {
        id = "create:player_count",
        data = {
            count = n,
            exact = op.text == "=" and 0 or 1
        }
    }
end

function conditions.idle(next)
    local time = next(false, "number")
    time.unit = time.unit or "s"
    return {
        id = "create:idle",
        data = {
            value = assert(tonumber(time.text), "invalid number near " .. time.text),
            time_unit = assert(time.unit, "invalid unit near " .. time.text .. time.unit)
        }
    }
end

function conditions.unloaded() return {id = "create:unloaded", data = {}} end
function conditions.powered() return {id = "create:powered", data = {}} end

local function to(next)
    local dest = next()
    assert(dest.type == "string", "expected string near " .. dest.text)
    local bracket = next()
    assert(bracket.type == "symbol" and bracket.text == "{", "expected '{' near " .. dest.text)
    local entry = {
        instruction = {
            id = "create:destination",
            data = {
                text = dest.text
            }
        },
        conditions = {}
    }
    local andl = {}
    while true do
        local cond = next(true)
        if cond.type == "newline" or (cond.type == "symbol" and cond.text == ";") then
            if _G.next(andl) then entry.conditions[#entry.conditions+1] = andl end
            andl = {}
        elseif cond.type == "symbol" and cond.text == "," then

        elseif cond.type == "symbol" and cond.text == "}" then
            break
        elseif cond.type == "token" then
            if not conditions[cond.text] then error("unexpected " .. cond.text, 0) end
            andl[#andl+1] = conditions[cond.text](next)
        else error("unexpected " .. cond.text, 0) end
    end
    if next(andl) then entry.conditions[#entry.conditions+1] = andl end
    return entry
end

local function parse(tokens)
    local schedule = {entries = {}}
    local pos = 1
    local function next(nl, typ)
        local a
        repeat
            a = tokens[pos]
            pos = pos + 1
            if not a then error("unexpected eof", 0) end
        until nl or a.type ~= "newline"
        if typ and a.type ~= typ then error("expected " .. typ .. " near " .. a.text, 0) end
        return a
    end
    while true do
        if not tokens[pos] then break end
        local tok = next(false, "token")
        if tok.text == "cyclic" then schedule.cyclic = true
        elseif tok.text == "to" then
            schedule.entries[#schedule.entries+1] = to(next)
        elseif tok.text == "rename" then
            local name = next(false, "string")
            schedule.entries[#schedule.entries+1] = {
                instruction = "create:rename",
                data = {
                    text = name.text
                }
            }
        elseif tok.text == "throttle" then
            local num = next(false, "number")
            local n = assert(tonumber(num.text), "invalid number near " .. num.text)
            if n < 5 or n > 100 then error("invalid throttle value " .. n, 0) end
            schedule.entries[#schedule.entries+1] = {
                instruction = "create:throttle",
                data = {
                    value = n
                }
            }
        else error("unexpected " .. tok.text, 0) end
    end
    return schedule
end

return function(str) return parse(lex(str)) end

can this run doom?