Add minting sample

validators/samples/minting.ak

@@ -0,0 +1,42 @@
+use aiken/dict as dict
+use aiken/list as list
+use aiken/transaction.{Input, OutputReference, ScriptContext, Transaction} as tx
+use aiken/transaction/value.{AssetName, MintedValue, PolicyId}
+
+validator {
+  fn free_minting(_redeemer: Void, _ctx: ScriptContext) -> Bool {
+    True
+  }
+}
+
+type Mode {
+  Minting
+  Burning
+}
+
+validator(token_name: ByteArray, oref: OutputReference) {
+  fn nft(redeemer: Mode, ctx: ScriptContext) -> Bool {
+    expect tx.Mint(policy_id) = ctx.purpose
+
+    let Transaction { inputs, mint, .. } = ctx.transaction
+
+    when redeemer is {
+      Minting ->
+        has_utxo(oref, inputs)? && check_mint(policy_id, token_name, mint, 1)?
+      Burning -> check_mint(policy_id, token_name, mint, -1)?
+    }
+  }
+}
+
+fn has_utxo(oref: OutputReference, inputs: List<Input>) {
+  list.any(inputs, fn(input) { input.output_reference == oref })
+}
+
+fn check_mint(cs: PolicyId, tn: AssetName, mint: MintedValue, mint_qty: Int) {
+  expect [(asset_name, qty)] =
+    mint
+      |> value.from_minted_value
+      |> value.tokens(cs)
+      |> dict.to_list()
+  (qty == mint_qty)? && (asset_name == tn)?
+}