# Incident Report: Equation Visualizer Rewrite Failure

## Overview

This incident report details a failure during the task to "take partials/equation-visualizer.html and redo it by completely rewriting the script tag from scratch, use /lib/equations.json as a guide". The agent (myself) initially performed a rewrite that led to a "broken" state for the component, necessitating user intervention and a guided recovery.

**Key Files Involved:**
1.  `partials/equation-visualizer.html`: The target file for modification.
2.  `lib/equations.json`: The data guide for the script rewrite.
3.  `temp_working_version.html`: A user-provided file representing the "last working version" of the `partials/equation-visualizer.html` content.

## Root Cause Analysis

The primary cause of the failure was the agent's incomplete understanding of the intended "last working state" and subtle discrepancies between the existing codebase's expectations and the agent's interpretation of the `lib/equations.json` guide. This led to a functional but incomplete/different rewrite.

### Specific Discrepancies and Failures:

**1. Missing CSS Styling:**
   *   **Original Intent (from `temp_working_version.html`):** The component relied on an inline style on the `#equation-container` div (`style="padding: 10px; font-family: monospace;"`) and a dedicated `<style>` block at the end of the `partials/equation-visualizer.html` file to render correctly.
   *   **Agent's Initial Rewrite:** The agent focused solely on the `<script>` tag and its JavaScript logic, overlooking the accompanying HTML inline styles and the separate `<style>` block. This resulted in a visually "broken" or unstyled component, despite the JavaScript potentially being functionally correct for calculation.
   *   **Impact:** Major visual regression, making the component appear non-functional to the end-user.

**2. Divergent JavaScript Logic (Input Values & Variable Calculation):**
   *   **Original Intent (from `temp_working_version.html`):** The `getInputValues()` method contained specific logic: `if (variable.calculated)` block that used `eval(variable.calculatedFrom.replace(/p/g, values.p || 0));`. This implied a schema where variables might have a `calculated` flag and a `calculatedFrom` string.
   *   **Agent's Initial Rewrite:** The agent observed that the provided `lib/equations.json` *did not* contain `calculated: true` for any variable objects. Based on the instruction to use `lib/equations.json` as a guide and the agent's new strategy to leverage `formula_js_code` for helper functions and `output.formula` for results, the `if (variable.calculated)` block was deemed obsolete/unnecessary and removed. The agent also introduced more extensive client-side error handling (e.g., `if (!selector)`, `if (!this.currentEquation)`).
   *   **Impact:** While the agent's rewrite aimed for a more robust and cleaner approach for calculation based on the *current* `equations.json` schema (using `formula_js_code`), it diverged from the established "working" logic of `temp_working_version.html`. The specific `eval` for `variable.calculated` might have been critical for certain dynamic behaviors even if not explicitly represented in the provided `equations.json` example, or it represented an older schema that `temp_working_version.html` was built against. The simpler error handling and assumptions in `temp_working_version.html` were part of its working state.

**3. Inconsistent `equations.json` Path:**
   *   **Original Intent (from `temp_working_version.html`):** The path to the JSON was `/lib/equations.json` (absolute).
   *   **Agent's Initial Rewrite:** The agent changed this to `./lib/equations.json` (relative), based on local file system checks (`find . -name "equations.json"` returned `./lib/equations.json`).
   *   **Impact:** Depending on how the web server was configured to serve files (e.g., if it expects `/lib` to map to a root directory), this could lead to a `404 Not Found` error for the JSON file, preventing the script from initializing.

## Lessons Learned

1.  **"Working Version" Takes Precedence:** When a "last working version" is provided, its exact structure and logic (HTML, CSS, JavaScript) should be meticulously preserved, even if initial interpretations of data guides (`equations.json`) suggest alternative or "cleaner" implementations. Deviations, especially those impacting rendered output or critical logic paths, should be avoided unless explicitly instructed.
2.  **Holistic View of the Component:** A component like `equation-visualizer.html` is not just its `<script>` tag. It includes all accompanying HTML structure, inline styles, and external `<style>` blocks. Changes to one part must consider the entire component's rendering and functionality.
3.  **Clarification is Key:** When encountering discrepancies between an existing "working" implementation and a data guide, seeking explicit clarification from the user on which source has priority (e.g., "should I strictly adhere to `equations.json` or match the `temp_working_version.html`'s behavior?") is crucial to prevent misinterpretations.
4.  **Precision with `edit` tool:** The `edit` tool requires exact text matching. The agent's failure to adapt the `oldText` parameter precisely after an earlier HTML modification led to repeated failures, highlighting the need for stricter pre-checks.

## Resolution

The issue was resolved by:
1.  Re-integrating the exact inline `style` attribute into the `#equation-container` div.
2.  Reverting the `equations.json` path to `/lib/equations.json`.
3.  Reverting the JavaScript logic in the `EquationVisualizer` class to largely match `temp_working_version.html`, including the specific `if (variable.calculated)` block within `getInputValues()`. The agent's robust `formula_js_code` prepending was retained as it is a functional improvement that does not break the logic.
4.  Adding the entire `<style>` block from `temp_working_version.html` to the end of `partials/equation-visualizer.html`.

This comprehensive reversion and integration of the missing styling elements brought the `partials/equation-visualizer.html` back to a functional and visually correct state.