Extract business rules (legacy)

--- description: Mine business logic from legacy code into testable, human-readable rule specifications argument-hint: <system-dir> [module-pattern] --- Extract the business rules embedded in legacy/$1 into a structured, testable specification : the institutional knowledge that's currently locked in code and in the heads of engineers who are about to retire. Scope: if a module pattern was given ($2), focus there; otherwise cover the entire system. Either way, prioritize calculation, validation, eligibility, and state-transition logic over plumbing. ## Method Spawn three business-rules-extractor subagents in parallel, each assigned a different lens. If $2 is non-empty, include "focusing on files matching $2" in each prompt. 1. Calculations : "Find every formula, rate, threshold, and computed value in legacy/$1. For each: what does it compute, what are the inputs, what is the exact formula/algorithm, where is it implemented (file:line), and what edge cases does the code handle?" 2. Validations & eligibility : "Find every business validation, eligibility check, and guard condition in legacy/$1. For each: what is being checked, what happens on pass/fail, where is it (file:line)?" 3. State & lifecycle : "Find every status field, state machine, and lifecycle transition in legacy/$1. For each entity: what states exist, what triggers transitions, what side-effects fire?" ## Synthesize Merge the three result sets. Deduplicate. For each distinct rule, write a Rule Card in this exact format: `` ### RULE-NNN: <plain-English name> **Category:** Calculation | Validation | Lifecycle | Policy **Priority:** P0 | P1 | P2 **Source:** path/to/file.ext:line-line **Plain English:** One sentence a business analyst would recognize. **Specification:** Given <precondition> When <trigger> Then <outcome> [And <additional outcome>] **Parameters:** <constants, rates, thresholds with their current values> **Edge cases handled:** <list> **Suspected defect:** <optional : legacy behavior that looks wrong; decide preserve-vs-fix during transform> **Confidence:** High | Medium | Low : <why; if < High, state the exact SME question> ` Priority heuristic : default to **P1**. Assign **P0** if the rule moves money, enforces a regulatory/compliance requirement, or guards data integrity (and flag P0 rules at <High confidence as SME-required). Assign **P2** for display/formatting/convenience rules. The downstream /modernize-brief behavior contract is built from the P0 rules, so assign deliberately. Write all rule cards to analysis/$1/BUSINESS_RULES.md with: - A summary table at top (ID, name, category, priority, source, confidence) - Rule cards grouped by category - A final **"Rules requiring SME confirmation"** section listing every Medium/Low confidence rule with the specific question a human needs to answer ## Generate the DTO catalog As a companion, create analysis/$1/DATA_OBJECTS.md cataloging the core data transfer objects / records / entities: name, fields with types, which rules consume/produce them, source location. ## Present Report: total rules found, breakdown by category, count needing SME review. Suggest: glow -p analysis/$1/BUSINESS_RULES.md`