Added ATR and expression fact plus cloning params (#6)

lib/facts/base.js

@@ -1,3 +1,4 @@
+const _ = require('lodash')
 const { ValidationError } = require('../errors')
 const { validate } = require('../validator')
 
@@ -18,7 +19,9 @@ class Fact {
     return {}
   }
 
-  value (params = {}) {
+  value (originalParams = {}) {
+    const params = _.cloneDeep(originalParams)
+
     this.#validateAndSanitize(params)
 
     return params

lib/facts/expression.js

@@ -0,0 +1,33 @@
+const jsonata = require('jsonata')
+
+const Fact = require('./base')
+
+class Expression extends Fact {
+  get id () {
+    return 'expression'
+  }
+
+  get name () {
+    return 'Evaluate Expression'
+  }
+
+  get description () {
+    return 'Evaluate an expression against provided paramters.'
+  }
+
+  get schema () {
+    return {
+      expression: { type: 'string', required: true, description: 'The expression.' },
+      data: { type: 'object', optional: true, default: {}, description: 'The data to evaluate the expression against.' },
+      $$strict: true
+    }
+  }
+
+  async value (params = {}) {
+    params = super.value(params)
+
+    return jsonata(params.expression).evaluate(params.data)
+  }
+}
+
+module.exports = Expression

lib/facts/index.js

@@ -1,4 +1,5 @@
 module.exports = {
   ta: require('./ta'),
-  market: require('./market')
+  market: require('./market'),
+  expression: require('./expression')
 }

lib/facts/ta/atr.js

@@ -0,0 +1,57 @@
+const _ = require('lodash')
+const BigNumber = require('bignumber.js')
+const techIndicators = require('technicalindicators')
+
+const Fact = require('../base')
+
+class ATR extends Fact {
+  get id () {
+    return 'ta.atr'
+  }
+
+  get name () {
+    return 'Average True Range (ATR)'
+  }
+
+  get description () {
+    return 'Calculate the Average True Range from values over period'
+  }
+
+  get schema () {
+    return {
+      values: {
+        type: 'array',
+        items: {
+          type: 'object',
+          props: {
+            high: { type: 'number', required: true, convert: true, description: 'The open value' },
+            low: { type: 'number', required: true, convert: true, description: 'The high value' },
+            close: { type: 'number', required: true, convert: true, description: 'The low value' }
+          },
+          strict: 'remove',
+          convert: true
+        },
+        optional: true,
+        default: [],
+        description: 'Values to apply indicator to.'
+      },
+      period: { type: 'number', optional: true, default: 14, min: 1, convert: true, description: 'The period to calculate.' },
+      $$strict: 'remove'
+    }
+  }
+
+  async value (params = {}) {
+    params = super.value(params)
+
+    const atr = techIndicators.ATR.calculate({
+      high: params.values.map(v => BigNumber(v.high).toNumber()),
+      low: params.values.map(v => BigNumber(v.low).toNumber()),
+      close: params.values.map(v => BigNumber(v.close).toNumber()),
+      period: params.period
+    })
+
+    return _.takeRight(atr, params.period)
+  }
+}
+
+module.exports = ATR

lib/facts/ta/index.js

@@ -1,6 +1,7 @@
 module.exports = {
   ema: require('./ema'),
   sma: require('./sma'),
+  atr: require('./atr'),
   rsi: require('./rsi'),
   crossUp: require('./crossUp'),
   crossDown: require('./crossDown')

lib/strategyEngine.js

@@ -12,7 +12,7 @@ class StrategyEngine {
     this.#validateAndSanitizeOpts(opts)
 
     this.engine = new Engine(undefined, {
-      pathResolver: (object, path) => jsonata(path).evaluate(object)
+      pathResolver: (data, path) => jsonata(path).evaluate(data)
     })
 
     opts.rules.forEach(rule => {

test/facts/expression.spec.js

@@ -0,0 +1,67 @@
+const { expect } = require('../helpers')
+const Expression = require('../../lib/facts/expression')
+
+describe('Fact expression', () => {
+  describe('#value', () => {
+    const fact = new Expression()
+
+    describe('params', () => {
+      const defaultParams = {
+        expression: 'a + b',
+        data: { a: 1, b: 2 }
+      }
+
+      describe('expression', () => {
+        it('is required', async () => {
+          let thrownErr = null
+
+          try {
+            await fact.value({ ...defaultParams, expression: undefined })
+          } catch (err) {
+            thrownErr = err
+          }
+
+          expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+          expect(thrownErr.data[0].message).to.eql('expression is required')
+        })
+
+        it('must a string', async () => {
+          let thrownErr = null
+
+          try {
+            await fact.value({ ...defaultParams, expression: {} })
+          } catch (err) {
+            thrownErr = err
+          }
+
+          expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+          expect(thrownErr.data[0].message).to.eql('expression must be a string')
+        })
+      })
+
+      describe('data', () => {
+        it('must be an object', async () => {
+          let thrownErr = null
+
+          try {
+            await fact.value({ ...defaultParams, data: 'invalid' })
+          } catch (err) {
+            thrownErr = err
+          }
+
+          expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+          expect(thrownErr.data[0].message).to.eql('data must be an Object')
+        })
+      })
+    })
+
+    it('evaluates expression against provided data', async () => {
+      const result = await fact.value({
+        expression: 'a + b',
+        data: { a: 1, b: 2 }
+      })
+
+      expect(result).to.eql(3)
+    })
+  })
+})

test/facts/ta/atr.spec.js

@@ -0,0 +1,179 @@
+const { expect } = require('../../helpers')
+const ATR = require('../../../lib/facts/ta/atr')
+
+describe('Fact ta.atr', () => {
+  describe('#value', () => {
+    const fact = new ATR()
+    const defaultParams = {
+      values: [
+        { high: 48.70, low: 47.79, close: 48.16 },
+        { high: 48.72, low: 48.14, close: 48.61 },
+        { high: 48.90, low: 48.39, close: 48.75 },
+        { high: 48.87, low: 48.37, close: 48.63 },
+        { high: 48.82, low: 48.24, close: 48.74 },
+        { high: 49.05, low: 48.64, close: 49.03 },
+        { high: 49.20, low: 48.94, close: 49.07 },
+        { high: 49.35, low: 48.86, close: 49.32 },
+        { high: 49.92, low: 49.50, close: 49.91 },
+        { high: 50.19, low: 49.87, close: 50.13 },
+        { high: 50.12, low: 49.20, close: 49.53 },
+        { high: 49.66, low: 48.90, close: 49.50 },
+        { high: 49.88, low: 49.43, close: 49.75 },
+        { high: 50.19, low: 49.73, close: 50.03 },
+        { high: 50.36, low: 49.26, close: 50.31 }
+      ],
+      period: 14
+    }
+
+    describe('params', () => {
+      describe('values', () => {
+        it('defaults to an empty array', async () => {
+          const result = await fact.value()
+
+          expect(result).to.eql([])
+        })
+
+        describe('props', () => {
+          describe('high', () => {
+            it('is required', async () => {
+              let thrownErr = null
+
+              try {
+                await fact.value({ ...defaultParams, values: [{ ...defaultParams.values[0], high: undefined }] })
+              } catch (err) {
+                thrownErr = err
+              }
+
+              expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+              expect(thrownErr.data[0].message).to.eql('values[0].high is required')
+            })
+
+            it('must be a number', async () => {
+              let thrownErr = null
+
+              try {
+                await fact.value({ ...defaultParams, values: [{ ...defaultParams.values[0], high: {} }] })
+              } catch (err) {
+                thrownErr = err
+              }
+
+              expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+              expect(thrownErr.data[0].message).to.eql('values[0].high must be a number')
+            })
+          })
+
+          describe('low', () => {
+            it('is required', async () => {
+              let thrownErr = null
+
+              try {
+                await fact.value({ ...defaultParams, values: [{ ...defaultParams.values[0], low: undefined }] })
+              } catch (err) {
+                thrownErr = err
+              }
+
+              expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+              expect(thrownErr.data[0].message).to.eql('values[0].low is required')
+            })
+
+            it('must be a number', async () => {
+              let thrownErr = null
+
+              try {
+                await fact.value({ ...defaultParams, values: [{ ...defaultParams.values[0], low: {} }] })
+              } catch (err) {
+                thrownErr = err
+              }
+
+              expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+              expect(thrownErr.data[0].message).to.eql('values[0].low must be a number')
+            })
+          })
+
+          describe('close', () => {
+            it('is required', async () => {
+              let thrownErr = null
+
+              try {
+                await fact.value({ ...defaultParams, values: [{ ...defaultParams.values[0], close: undefined }] })
+              } catch (err) {
+                thrownErr = err
+              }
+
+              expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+              expect(thrownErr.data[0].message).to.eql('values[0].close is required')
+            })
+
+            it('must be a number', async () => {
+              let thrownErr = null
+
+              try {
+                await fact.value({ ...defaultParams, values: [{ ...defaultParams.values[0], close: {} }] })
+              } catch (err) {
+                thrownErr = err
+              }
+
+              expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+              expect(thrownErr.data[0].message).to.eql('values[0].close must be a number')
+            })
+          })
+        })
+      })
+
+      describe('period', () => {
+        it('defaults to 14', async () => {
+          const result = await fact.value(defaultParams)
+
+          expect(result).to.eql([0.5678571428571431])
+        })
+
+        it('must be an number', async () => {
+          let thrownErr = null
+
+          try {
+            await fact.value({ period: 'ten' })
+          } catch (err) {
+            thrownErr = err
+          }
+
+          expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+          expect(thrownErr.data[0].message).to.eql('period must be a number')
+        })
+
+        it('must be at least 1', async () => {
+          let thrownErr = null
+
+          try {
+            await fact.value({ period: 0 })
+          } catch (err) {
+            thrownErr = err
+          }
+
+          expect(thrownErr.type).to.eql('VALIDATION_ERROR')
+          expect(thrownErr.data[0].message).to.eql('period must be greater than or equal to 1')
+        })
+      })
+    })
+
+    it('returns the ATR', async () => {
+      const result = await fact.value(defaultParams)
+
+      expect(result).to.eql([0.5678571428571431])
+    })
+
+    it('only returns up to periods', async () => {
+      const result = await fact.value({
+        values: defaultParams.values,
+        period: 5
+      })
+
+      expect(result).to.eql([
+        0.5545580800000003,
+        0.5956464639999999,
+        0.5665171712000004,
+        0.5452137369600005,
+        0.6561709895680007
+      ])
+    })
+  })
+})