Add a blueprint policy command

Computes the policy ID of a minting policy; added guards for blueprint address to check that it's not a minting policy; Wasn't 100% sure where the errors should live, so I'm happy to move them if there's objections

crates/aiken/src/cmd/blueprint/mod.rs

@@ -1,4 +1,5 @@
 pub mod address;
+pub mod policy;
 pub mod apply;
 pub mod convert;
 
@@ -8,6 +9,7 @@ use clap::Subcommand;
 #[derive(Subcommand)]
 pub enum Cmd {
     Address(address::Args),
+    Policy(policy::Args),
     Apply(apply::Args),
     Convert(convert::Args),
 }
@@ -15,6 +17,7 @@ pub enum Cmd {
 pub fn exec(cmd: Cmd) -> miette::Result<()> {
     match cmd {
         Cmd::Address(args) => address::exec(args),
+        Cmd::Policy(args) => policy::exec(args),
         Cmd::Apply(args) => apply::exec(args),
         Cmd::Convert(args) => convert::exec(args),
     }

crates/aiken/src/cmd/blueprint/policy.rs

@@ -0,0 +1,55 @@
+use crate::with_project;
+use aiken_lang::ast::Tracing;
+use std::path::PathBuf;
+
+/// Compute a validator's address.
+#[derive(clap::Args)]
+pub struct Args {
+    /// Path to project
+    directory: Option<PathBuf>,
+
+    /// Name of the validator's module within the project. Optional if there's only one validator
+    #[clap(short, long)]
+    module: Option<String>,
+
+    /// Name of the validator within the module. Optional if there's only one validator
+    #[clap(short, long)]
+    validator: Option<String>,
+
+    /// Force the project to be rebuilt, otherwise relies on existing artifacts (i.e. plutus.json)
+    #[clap(long)]
+    rebuild: bool,
+}
+
+pub fn exec(
+    Args {
+        directory,
+        module,
+        validator,
+        rebuild,
+    }: Args,
+) -> miette::Result<()> {
+    with_project(directory, |p| {
+        if rebuild {
+            p.build(false, Tracing::NoTraces)?;
+        }
+
+        let title = module.as_ref().map(|m| {
+            format!(
+                "{m}{}",
+                validator
+                    .as_ref()
+                    .map(|v| format!(".{v}"))
+                    .unwrap_or_default()
+            )
+        });
+
+        let title = title.as_ref().or(validator.as_ref());
+
+        let policy = p.policy(title)?;
+
+        println!("{}", policy);
+
+        Ok(())
+    })
+}