type storage = int;

type parameter =
| ["Increment", int]
| ["Decrement", int]
| ["Reset"];

/* Two entrypoints */

const add = (store: storage, delta: int) => store + delta;
const sub = (store: storage, delta: int) => store - delta;

/* Main access point that dispatches to the entrypoints according to
   the smart contract parameter. */

const main = (action: parameter, store: storage) : [ list<operation> , storage ] => {
 return [
   list([]),    // No operations
   (match (action, {
    Increment: n => add (store, n),
    Decrement: n => sub (store, n),
    Reset:     ()  => 0}))
  ]
};

/* Tests for main access point */

const test_initial_storage = (() => {
  let initial_storage = 42;
  let [taddr, _, _] = Test.originate(main, initial_storage, 0 as tez);
  return assert(Test.get_storage(taddr) == initial_storage)
}) ();

const test_increment = (() => {
  let initial_storage = 42;
  let [taddr, _, _] = Test.originate(main, initial_storage, 0 as tez);
  let contr = Test.to_contract(taddr);
  let _ = Test.transfer_to_contract_exn(contr, (Increment (1)), 1 as mutez);
  return assert(Test.get_storage(taddr) == initial_storage + 1);
}) ();

type storage = int

type parameter =
  Increment of int
| Decrement of int
| Reset

// Two entrypoints

let add (store : storage) (delta : int) = store + delta
let sub (store : storage) (delta : int) = store - delta

(* Main access point that dispatches to the entrypoints according to
   the smart contract parameter. *)

let main (action : parameter) (store : storage) : operation list * storage =
 [],    // No operations
 (match action with
   Increment (n) -> add store n
 | Decrement (n) -> sub store n
 | Reset         -> 0)

(* Tests for main access point *)

let initial_storage = 42

let test_initial_storage =
 let (taddr, _, _) = Test.originate main initial_storage 0tez in
 assert (Test.get_storage taddr = initial_storage)

let test_increment =
 let (taddr, _, _) = Test.originate main initial_storage 0tez in
 let contr = Test.to_contract taddr in
 let _ = Test.transfer_to_contract_exn contr (Increment 1) 1mutez in
 assert (Test.get_storage taddr = initial_storage + 1)