From b12c9892ec3c18646fb7f39d5376257eb641fc8d Mon Sep 17 00:00:00 2001
From: Robert Sesek <rsesek@bluestatic.org>
Date: Sun, 15 Mar 2020 15:19:47 -0400
Subject: [PATCH] First cut at a Trace system.

---
 src/core/Form.ts        |  2 ++
 src/core/Line.ts        | 28 +++++++++++++++----
 src/core/Trace.ts       | 61 +++++++++++++++++++++++++++++++++++++++++
 src/fed2019/Form8949.ts |  3 ++
 4 files changed, 88 insertions(+), 6 deletions(-)
 create mode 100644 src/core/Trace.ts

diff --git a/src/core/Form.ts b/src/core/Form.ts
index 4f3124b..6515753 100644
--- a/src/core/Form.ts
+++ b/src/core/Form.ts
@@ -5,6 +5,7 @@
 
 import Person from './Person';
 import TaxReturn from './TaxReturn';
+import Trace from './Trace';
 import { Line } from './Line';
 import { InconsistencyError, NotFoundError } from './Errors';
 
@@ -53,6 +54,7 @@ export default abstract class Form<L extends { [key: string]: Line<any> },
     if (!(name in this._input)) {
       throw new NotFoundError(`No input with key ${name} on form ${this.name}`);
     }
+    Trace.add(`${this.name}-input-${name}`);
     return this._input[name];
   }
 
diff --git a/src/core/Line.ts b/src/core/Line.ts
index b0d6515..ca5dd00 100644
--- a/src/core/Line.ts
+++ b/src/core/Line.ts
@@ -4,6 +4,7 @@
 // SPDX-License-Identifier: GPL-3.0-only
 
 import TaxReturn from './TaxReturn';
+import Trace from './Trace';
 import Form, { FormClass } from './Form';
 
 export abstract class Line<T> {
@@ -38,7 +39,10 @@ export class ComputedLine<T> extends Line<T> {
   }
 
   value(tr: TaxReturn): T {
-    return this._compute(tr);
+    const trace = new Trace(this);
+    const value = this._compute(tr);
+    trace.end();
+    return value;
   }
 };
 
@@ -61,10 +65,14 @@ export class ReferenceLine<F extends Form<any>,
   }
 
   value(tr: TaxReturn): T {
+    const trace = new Trace(this);
     const form: F = tr.findForm(this._form);
-    if (this._fallback !== undefined && !form)
+    if (this._fallback !== undefined && !form) {
+      trace.end();
       return this._fallback;
+    }
     const value: T = form.getValue(tr, this._line);
+    trace.end();
     return value;
   }
 };
@@ -82,9 +90,14 @@ export class InputLine<U = unknown, T extends keyof U = any> extends Line<U[T]>
   }
 
   value(tr: TaxReturn): U[T] {
-    if (!this.form.hasInput(this._input) && this._fallback !== undefined)
+    const trace = new Trace(this);
+    if (!this.form.hasInput(this._input) && this._fallback !== undefined) {
+      trace.end();
       return this._fallback;
-    return this.form.getInput<T>(this._input);
+    }
+    const value = this.form.getInput<T>(this._input);
+    trace.end();
+    return value;
   }
 };
 
@@ -95,14 +108,17 @@ export class AccumulatorLine<F extends Form<any>,
   private _line: L;
 
   constructor(form: FormClass<F>, line: L, description?: string) {
-    super(description || `Accumulator F${form}.L${line}`);
+    super(description || `Accumulator F${form.name}.L${line}`);
     this._form = form;
     this._line = line;
   }
 
   value(tr): number {
+    const trace = new Trace(this);
     const forms: F[] = tr.findForms(this._form);
-    return sumLineOfForms(tr, forms, this._line);
+    const value = sumLineOfForms(tr, forms, this._line);
+    trace.end();
+    return value;
   }
 };
 
diff --git a/src/core/Trace.ts b/src/core/Trace.ts
new file mode 100644
index 0000000..b94fac8
--- /dev/null
+++ b/src/core/Trace.ts
@@ -0,0 +1,61 @@
+// Copyright 2020 Blue Static <https://www.bluestatic.org>
+// This program is free software licensed under the GNU General Public License,
+// version 3.0. The full text of the license can be found in LICENSE.txt.
+// SPDX-License-Identifier: GPL-3.0-only
+
+import { Line } from './Line';
+
+var current: Trace = null;
+
+var traces: Trace[] = [];
+
+export default class Trace {
+  private _stack: Set<string>[] = [];
+  private _index = 0;
+  private _name: string;
+
+  constructor(line: Line<any>) {
+    this._name = this._formatLine(line);
+    const s = new Set<string>();
+
+    s.add(`Start: ${this._name}`);
+
+    if (current === null) {
+      current = this;
+    } else {
+      ++current._index;
+    }
+
+    current._stack.push(s);
+  }
+
+  static add(id: string) {
+    if (current === null)
+      return;
+    current._stack[current._index].add(id);
+  }
+
+  end() {
+    --current._index;
+    if (current === this) {
+      current = null;
+      traces.push(this);
+    }
+  }
+
+  get traceList(): readonly string[][] {
+    return this._stack.map(s => [...s.values()]);
+  }
+
+  private _formatLine(line: Line<any>): string {
+    if (line.form === undefined)
+      return `${line.constructor.name} (${line.description})`;
+    return `${line.form.name}-${line.id} (${line.description})`;
+  }
+};
+
+export function getLastTraceList(): readonly string[][] {
+  if (traces.length == 0)
+    return null;
+  return traces[traces.length - 1].traceList;
+}
diff --git a/src/fed2019/Form8949.ts b/src/fed2019/Form8949.ts
index ea9b266..53e5c21 100644
--- a/src/fed2019/Form8949.ts
+++ b/src/fed2019/Form8949.ts
@@ -3,6 +3,7 @@
 // version 3.0. The full text of the license can be found in LICENSE.txt.
 // SPDX-License-Identifier: GPL-3.0-only
 
+import Trace from '../core/Trace';
 import { Form, Person, TaxReturn } from '../core';
 import { Line, InputLine, ComputedLine, sumLineOfForms } from '../core/Line';
 
@@ -64,6 +65,7 @@ class Form8949Line extends Line<Form8949Total> {
   }
 
   value(tr: TaxReturn): Form8949Total {
+    const trace = new Trace(this);
     const f1099bs = matching1099Bs(tr, this._box);
     const proceeds = sumLineOfForms(tr, f1099bs, '1d');
     const costBasis = sumLineOfForms(tr, f1099bs, '1e');
@@ -72,6 +74,7 @@ class Form8949Line extends Line<Form8949Total> {
         f8949.getInput('adjustments')
           .filter(a => f1099bs.includes(a.entry))
           .reduce((acc, curr) => acc + curr.amount, 0);
+    trace.end();
     return {
       proceeds,
       costBasis,
-- 
2.22.5