open Parser
open Evaluator
open System.IO

let usage() =
    printfn "Usage: dotnet run <file> [debug]"
    printfn "where"
    printfn "   <file> is a Blub program"
    printfn "  [debug] is \"true\" or \"false\" (or false if omitted)"
    exit 1

[<EntryPoint>]
let main argv : int =
    (* Check for proper usage *)
    if argv.Length <> 1 && argv.Length <> 2 then
        usage()

    (* read in the input file *)
    let file = argv[0]
    if not (System.IO.File.Exists file) then
        printfn $"ERROR: Cannot find file '{file}'."
        usage()

    let input = File.ReadAllText file

    (* does the user want parser debugging turned on? *)
    let do_debug = if argv.Length = 2 && argv[1] = "true" then true else false

    (* try to parse what they gave us *)
    let ast_maybe = parse input do_debug

    (* try to evaluate what we parsed... or not *)
    match ast_maybe with
    | Some ast ->
        eval ast Map.empty |> ignore
        0
    | None     ->
        printfn "Invalid program."
        1