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<h1 class="menu-title">towl Documentation</h1>
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<h1 id="api-overview"><a class="header" href="#api-overview">API Overview</a></h1>
<p>towl is structured as a library (<code>towl</code> crate) with a thin binary wrapper. The library exposes modules for configuration, scanning, parsing, output, and error handling.</p>
<h2 id="module-map"><a class="header" href="#module-map">Module Map</a></h2>
<pre><code class="language-text">towl (lib)
├── cli Command-line argument parsing (clap)
├── comment TODO types and comment structures
│ ├── todo TodoType enum, TodoComment struct
│ └── error TowlCommentError
├── config Configuration loading and validation
│ ├── types TowlConfig, ParsingConfig, GitHubConfig, Owner, Repo
│ ├── git GitRepoInfo (git remote discovery)
│ └── error TowlConfigError
├── scanner Directory walking and file filtering
│ ├── types Scanner, ScanResult
│ └── error TowlScannerError
├── parser Regex-based TODO extraction
│ ├── types Parser, Pattern
│ └── error TowlParserError
├── output Formatting and writing results
│ ├── formatter
│ │ ├── formatters CsvFormatter, JsonFormatter, MarkdownFormatter,
│ │ │ TableFormatter, TomlFormatter
│ │ └── error FormatterError
│ ├── writer
│ │ ├── writers StdoutWriter, FileWriter
│ │ └── error WriterError
│ └── error TowlOutputError
├── github GitHub issue creation
│ ├── client GitHubClient
│ ├── types CreatedIssue
│ └── error TowlGitHubError
├── processor TODO replacement with issue links
│ ├── types Processor, ProcessorResult
│ └── error TowlProcessorError
├── llm LLM-powered TODO validation
│ ├── analyse analyse_todos, gather_expanded_context
│ ├── claude ClaudeProvider (Anthropic API)
│ ├── openai OpenAiProvider (OpenAI-compatible API)
│ ├── cli ClaudeCodeProvider, CodexProvider (CLI agents)
│ ├── prompt System prompt and user content construction
│ ├── types AnalysisResult, AnalysisSummary, Validity, LlmUsage
│ └── error TowlLlmError
├── tui Interactive terminal UI
│ ├── app App, AppMode, SortField, PeekState
│ ├── input Action, handle_input
│ ├── render draw
│ └── error TowlTuiError
└── error Top-level TowlError (aggregates all error types)
</code></pre>
<h2 id="data-flow"><a class="header" href="#data-flow">Data Flow</a></h2>
<pre><code class="language-text">TowlConfig ──► Scanner ──► Parser ──► Output
│ │ │ │
│ │ │ ├─ FormatterImpl (enum dispatch)
│ │ │ └─ WriterImpl (enum dispatch)
│ │ │
│ │ └─ Vec<TodoComment>
│ │
│ └─ ScanResult { todos, files_scanned, ... }
│
├─ ParsingConfig + GitHubConfig + LlmConfig
│
└─ LlmConfig ──► LlmProvider ──► analyse_todos ──► AnalysisSummary
</code></pre>
<h2 id="key-types"><a class="header" href="#key-types">Key Types</a></h2>
<div class="table-wrapper"><table><thead><tr><th>Type</th><th>Module</th><th>Purpose</th></tr></thead><tbody>
<tr><td><code>TowlConfig</code></td><td><code>config</code></td><td>Top-level configuration container</td></tr>
<tr><td><code>ParsingConfig</code></td><td><code>config</code></td><td>File extensions, patterns, context lines</td></tr>
<tr><td><code>GitHubConfig</code></td><td><code>config</code></td><td>Owner, repo, token</td></tr>
<tr><td><code>Scanner</code></td><td><code>scanner</code></td><td>Directory walk + file filtering</td></tr>
<tr><td><code>ScanResult</code></td><td><code>scanner</code></td><td>Structured scan output with metrics</td></tr>
<tr><td><code>Parser</code></td><td><code>parser</code></td><td>Regex-based TODO extraction</td></tr>
<tr><td><code>TodoComment</code></td><td><code>comment</code></td><td>A single extracted TODO item</td></tr>
<tr><td><code>TodoType</code></td><td><code>comment</code></td><td>Enum: Todo, Fixme, Hack, Note, Bug</td></tr>
<tr><td><code>Output</code></td><td><code>output</code></td><td>Formatter + writer combination</td></tr>
<tr><td><code>GitHubClient</code></td><td><code>github</code></td><td>Authenticated GitHub API client</td></tr>
<tr><td><code>CreatedIssue</code></td><td><code>github</code></td><td>Metadata for a created GitHub issue</td></tr>
<tr><td><code>Processor</code></td><td><code>processor</code></td><td>Replaces TODOs with issue links in source files</td></tr>
<tr><td><code>ProcessorResult</code></td><td><code>processor</code></td><td>Summary of a batch replacement operation</td></tr>
<tr><td><code>LlmProvider</code></td><td><code>llm</code></td><td>Enum-dispatched LLM provider (Claude, OpenAI, CLI agents)</td></tr>
<tr><td><code>AnalysisResult</code></td><td><code>llm</code></td><td>LLM validation result for a single TODO</td></tr>
<tr><td><code>AnalysisSummary</code></td><td><code>llm</code></td><td>Aggregate counts from a batch analysis run</td></tr>
<tr><td><code>Validity</code></td><td><code>llm</code></td><td>TODO validity classification (Valid, Invalid, Uncertain)</td></tr>
<tr><td><code>App</code></td><td><code>tui</code></td><td>TUI application state and mode management</td></tr>
<tr><td><code>AppMode</code></td><td><code>tui</code></td><td>Current UI mode (Browse, Peek, Confirm, etc.)</td></tr>
<tr><td><code>TowlError</code></td><td><code>error</code></td><td>Top-level error aggregating all sub-errors</td></tr>
</tbody></table>
</div>
<h2 id="error-hierarchy"><a class="header" href="#error-hierarchy">Error Hierarchy</a></h2>
<pre><code class="language-text">TowlError
├── TowlConfigError Config loading, TOML parsing, git discovery
├── TowlScannerError File walk, I/O, resource limits
│ └── TowlParserError Regex compilation, pattern validation
├── TowlOutputError Formatting, file writing
│ ├── FormatterError Serialisation failures
│ └── WriterError I/O, path traversal
├── TowlGitHubError API errors, auth, rate limiting
├── TowlProcessorError File replacement errors
├── TowlTuiError Terminal I/O errors
└── TowlLlmError LLM API, auth, parsing, I/O
</code></pre>
<p>All error types use <code>thiserror</code> for <code>Display</code> and <code>Error</code> trait implementations. Conversion between levels uses <code>#[from]</code> attributes for ergonomic <code>?</code> propagation.</p>
<h2 id="constants"><a class="header" href="#constants">Constants</a></h2>
<div class="table-wrapper"><table><thead><tr><th>Name</th><th>Value</th><th>Module</th><th>Purpose</th></tr></thead><tbody>
<tr><td><code>MAX_FILE_SIZE</code></td><td>10 MB</td><td>scanner</td><td>Skip oversized files</td></tr>
<tr><td><code>MAX_TODO_COUNT</code></td><td>10,000</td><td>scanner</td><td>Per-file TODO cap</td></tr>
<tr><td><code>MAX_TOTAL_TODO_COUNT</code></td><td>100,000</td><td>scanner</td><td>Global TODO cap</td></tr>
<tr><td><code>MAX_FILES_SCANNED</code></td><td>100,000</td><td>scanner</td><td>Directory walk cap</td></tr>
<tr><td><code>MAX_PATTERN_LENGTH</code></td><td>256 chars</td><td>parser</td><td>Regex length limit</td></tr>
<tr><td><code>REGEX_SIZE_LIMIT</code></td><td>256 KB</td><td>parser</td><td>Compiled regex size limit</td></tr>
<tr><td><code>MAX_TOTAL_PATTERNS</code></td><td>50</td><td>parser</td><td>Total patterns across all categories</td></tr>
<tr><td><code>MAX_CONFIG_PATTERNS</code></td><td>100</td><td>config</td><td>Per-field pattern array cap</td></tr>
<tr><td><code>DEFAULT_CONFIG_PATH</code></td><td><code>.towl.toml</code></td><td>config</td><td>Default config file</td></tr>
</tbody></table>
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