feat: implement 1st pass of space-time contract

.github/workflows/tests.yml

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+name: Tests
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: aiken-lang/setup-aiken@v0.1.0
+        with:
+          version: v1.0.24-alpha
+
+      - run: aiken fmt --check
+      - run: aiken check -D
+      - run: aiken build

.gitignore

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+# Aiken compilation artifacts
+artifacts/
+# Aiken's project working directory
+build/
+# Aiken's default documentation export
+docs/

aiken.lock

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+# This file was generated by Aiken
+# You typically do not need to edit this file
+
+[[requirements]]
+name = "aiken-lang/stdlib"
+version = "1.7.0"
+source = "github"
+
+[[packages]]
+name = "aiken-lang/stdlib"
+version = "1.7.0"
+requirements = []
+source = "github"
+
+[etags]

aiken.toml

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+name = "txpipe/asteria"
+version = "0.0.0"
+license = "Apache-2.0"
+description = "Aiken contracts for project 'txpipe/asteria'"
+
+[repository]
+user = "txpipe"
+project = "asteria"
+platform = "github"
+
+[[dependencies]]
+name = "aiken-lang/stdlib"
+version = "1.7.0"
+source = "github"

plutus.json

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+{
+  "preamble": {
+    "title": "txpipe/asteria",
+    "description": "Aiken contracts for project 'txpipe/asteria'",
+    "version": "0.0.0",
+    "plutusVersion": "v2",
+    "compiler": {
+      "name": "Aiken",
+      "version": "v1.0.24-alpha+982eff4"
+    },
+    "license": "Apache-2.0"
+  },
+  "validators": [
+    {
+      "title": "spacetime.spend",
+      "datum": {
+        "title": "datum",
+        "schema": {
+          "$ref": "#/definitions/spacetime~1Datum"
+        }
+      },
+      "redeemer": {
+        "title": "redeemer",
+        "schema": {
+          "$ref": "#/definitions/spacetime~1Redeemer"
+        }
+      },
+      "parameters": [
+        {
+          "title": "ship_policy_id",
+          "schema": {
+            "$ref": "#/definitions/ByteArray"
+          }
+        },
+        {
+          "title": "max_speed",
+          "schema": {
+            "$ref": "#/definitions/Int"
+          }
+        },
+        {
+          "title": "fuel_per_step",
+          "schema": {
+            "$ref": "#/definitions/Int"
+          }
+        }
+      ],
+      "compiledCode": "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",
+      "hash": "4169f9c7110ee486b5e1872d123b10aa4924f38c8a47291b5d8e3422"
+    }
+  ],
+  "definitions": {
+    "ByteArray": {
+      "dataType": "bytes"
+    },
+    "Int": {
+      "dataType": "integer"
+    },
+    "spacetime/Datum": {
+      "title": "Datum",
+      "anyOf": [
+        {
+          "title": "Datum",
+          "dataType": "constructor",
+          "index": 0,
+          "fields": [
+            {
+              "title": "ship_id",
+              "$ref": "#/definitions/ByteArray"
+            },
+            {
+              "title": "pos_x",
+              "$ref": "#/definitions/Int"
+            },
+            {
+              "title": "pos_y",
+              "$ref": "#/definitions/Int"
+            },
+            {
+              "title": "fuel",
+              "$ref": "#/definitions/Int"
+            }
+          ]
+        }
+      ]
+    },
+    "spacetime/Redeemer": {
+      "title": "Redeemer",
+      "anyOf": [
+        {
+          "title": "Redeemer",
+          "dataType": "constructor",
+          "index": 0,
+          "fields": [
+            {
+              "title": "delta_x",
+              "$ref": "#/definitions/Int"
+            },
+            {
+              "title": "delta_y",
+              "$ref": "#/definitions/Int"
+            }
+          ]
+        }
+      ]
+    }
+  }
+}

validators/spacetime.ak

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+use aiken/list
+use aiken/math
+use aiken/transaction.{InlineDatum, ScriptContext, Spend, Transaction}
+use aiken/transaction/value.{PolicyId, quantity_of}
+
+type Datum {
+  ship_id: ByteArray,
+  pos_x: Int,
+  pos_y: Int,
+  fuel: Int,
+}
+
+type Redeemer {
+  delta_x: Int,
+  delta_y: Int,
+}
+
+fn distance(delta_x: Int, delta_y: Int) -> Int {
+  math.abs(delta_x) + math.abs(delta_y)
+}
+
+// we need to enforce:
+// [x] that the speed (manhattan_distance/slot) doesn't exceed an upper bound
+// [ ] that the ship has enough fuel (token) to move the desired delta
+// [ ] that the new position of the ship utxo equals the last position + delta
+// [ ] that the fuel required for the delta has been burned
+// [ ] that the tx is signed by the owner of the ship (token holder)
+
+validator(ship_policy_id: PolicyId, max_speed: Int, fuel_per_step: Int) {
+  fn spend(datum: Datum, redeemer: Redeemer, ctx: ScriptContext) -> Bool {
+    let Redeemer { delta_x, delta_y } = redeemer
+
+    let Datum { ship_id, pos_x, pos_y, fuel } = datum
+
+    let ScriptContext { transaction, purpose } = ctx
+
+    let Transaction { inputs, outputs, .. } = transaction
+
+    expect Spend(utxo_ref) = purpose
+
+    expect Some(own_input) =
+      list.find(inputs, fn(input) { input.output_reference == utxo_ref })
+
+    expect Some(own_output) =
+      list.find(
+        outputs,
+        fn(output) { quantity_of(output.value, ship_policy_id, ship_id) == 1 },
+      )
+
+    let must_hold_ship_asset =
+      quantity_of(own_input.output.value, ship_policy_id, ship_id) == 1
+
+    let distance = distance(delta_x, delta_y)
+
+    // speed = distance since we consider each block the unit of time 
+    let must_respect_max_speed = distance <= max_speed
+
+    let must_have_enough_fuel = fuel >= fuel_per_step * distance
+
+    expect InlineDatum(out_data) = own_output.datum
+
+    expect out_data: Datum = out_data
+
+    let final_pos_must_respect_movement =
+      out_data.pos_x == pos_x + delta_x && out_data.pos_y == pos_y + delta_y
+
+    let final_ship_id_must_match = out_data.ship_id == ship_id
+
+    must_hold_ship_asset && must_respect_max_speed && must_have_enough_fuel && final_pos_must_respect_movement && final_ship_id_must_match
+  }
+}