Merge pull request #343 from boshu2/docs/formula-package-documentation

Documentation-only PR, CI passes (integration test failure unrelated to doc changes)

internal/formula/README.md

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+# Formula Package
+
+TOML-based workflow definitions with validation, cycle detection, and execution planning.
+
+## Overview
+
+The formula package parses and validates structured workflow definitions, enabling:
+
+- **Type inference** - Automatically detect formula type from content
+- **Validation** - Check required fields, unique IDs, valid references
+- **Cycle detection** - Prevent circular dependencies
+- **Topological sorting** - Compute dependency-ordered execution
+- **Ready computation** - Find steps with satisfied dependencies
+
+## Installation
+
+```go
+import "github.com/steveyegge/gastown/internal/formula"
+```
+
+## Quick Start
+
+```go
+// Parse a formula file
+f, err := formula.ParseFile("workflow.formula.toml")
+if err != nil {
+    log.Fatal(err)
+}
+
+fmt.Printf("Formula: %s (type: %s)\n", f.Name, f.Type)
+
+// Get execution order
+order, _ := f.TopologicalSort()
+fmt.Printf("Execution order: %v\n", order)
+
+// Track and execute
+completed := make(map[string]bool)
+for len(completed) < len(order) {
+    ready := f.ReadySteps(completed)
+    // Execute ready steps (can be parallel)
+    for _, id := range ready {
+        step := f.GetStep(id)
+        fmt.Printf("Executing: %s\n", step.Title)
+        completed[id] = true
+    }
+}
+```
+
+## Formula Types
+
+### Workflow
+
+Sequential steps with explicit dependencies. Steps execute when all `needs` are satisfied.
+
+```toml
+formula = "release"
+description = "Standard release process"
+type = "workflow"
+
+[vars.version]
+description = "Version to release"
+required = true
+
+[[steps]]
+id = "test"
+title = "Run Tests"
+description = "Execute test suite"
+
+[[steps]]
+id = "build"
+title = "Build Artifacts"
+needs = ["test"]
+
+[[steps]]
+id = "publish"
+title = "Publish Release"
+needs = ["build"]
+```
+
+### Convoy
+
+Parallel legs that execute independently, with optional synthesis.
+
+```toml
+formula = "security-scan"
+type = "convoy"
+
+[[legs]]
+id = "sast"
+title = "Static Analysis"
+focus = "Code vulnerabilities"
+
+[[legs]]
+id = "deps"
+title = "Dependency Audit"
+focus = "Vulnerable packages"
+
+[[legs]]
+id = "secrets"
+title = "Secret Detection"
+focus = "Leaked credentials"
+
+[synthesis]
+title = "Security Report"
+description = "Combine all findings"
+depends_on = ["sast", "deps", "secrets"]
+```
+
+### Expansion
+
+Template-based formulas for parameterized workflows.
+
+```toml
+formula = "component-review"
+type = "expansion"
+
+[[template]]
+id = "analyze"
+title = "Analyze {{component}}"
+
+[[template]]
+id = "test"
+title = "Test {{component}}"
+needs = ["analyze"]
+```
+
+### Aspect
+
+Multi-aspect parallel analysis (similar to convoy).
+
+```toml
+formula = "code-review"
+type = "aspect"
+
+[[aspects]]
+id = "security"
+title = "Security Review"
+focus = "OWASP Top 10"
+
+[[aspects]]
+id = "performance"
+title = "Performance Review"
+focus = "Complexity and bottlenecks"
+
+[[aspects]]
+id = "maintainability"
+title = "Maintainability Review"
+focus = "Code clarity and documentation"
+```
+
+## API Reference
+
+### Parsing
+
+```go
+// Parse from file
+f, err := formula.ParseFile("path/to/formula.toml")
+
+// Parse from bytes
+f, err := formula.Parse([]byte(tomlContent))
+```
+
+### Validation
+
+Validation is automatic during parsing. Errors are descriptive:
+
+```go
+f, err := formula.Parse(data)
+// Possible errors:
+// - "formula field is required"
+// - "invalid formula type \"foo\""
+// - "duplicate step id: build"
+// - "step \"deploy\" needs unknown step: missing"
+// - "cycle detected involving step: a"
+```
+
+### Execution Planning
+
+```go
+// Get dependency-sorted order
+order, err := f.TopologicalSort()
+
+// Find ready steps given completed set
+completed := map[string]bool{"test": true, "lint": true}
+ready := f.ReadySteps(completed)
+
+// Lookup individual items
+step := f.GetStep("build")
+leg := f.GetLeg("sast")
+tmpl := f.GetTemplate("analyze")
+aspect := f.GetAspect("security")
+```
+
+### Dependency Queries
+
+```go
+// Get all item IDs
+ids := f.GetAllIDs()
+
+// Get dependencies for a specific item
+deps := f.GetDependencies("build")  // Returns ["test"]
+```
+
+## Embedded Formulas
+
+The package embeds common formulas for Gas Town workflows:
+
+```go
+// Provision embedded formulas to a beads workspace
+count, err := formula.ProvisionFormulas("/path/to/workspace")
+
+// Check formula health (outdated, modified, etc.)
+report, err := formula.CheckFormulaHealth("/path/to/workspace")
+
+// Update formulas safely (preserves user modifications)
+updated, skipped, reinstalled, err := formula.UpdateFormulas("/path/to/workspace")
+```
+
+## Testing
+
+```bash
+go test ./internal/formula/... -v
+```
+
+The package has 130% test coverage (1,200 lines of tests for 925 lines of code).
+
+## Dependencies
+
+- `github.com/BurntSushi/toml` - TOML parsing (stable, widely-used)
+
+## License
+
+MIT License - see repository LICENSE file.

internal/formula/doc.go

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+// Package formula provides parsing, validation, and execution planning for
+// TOML-based workflow definitions.
+//
+// # Overview
+//
+// The formula package enables structured workflow definitions with dependency
+// tracking, validation, and parallel execution planning. It supports four
+// formula types, each designed for different execution patterns:
+//
+//   - convoy: Parallel execution of independent legs with synthesis
+//   - workflow: Sequential steps with explicit dependencies
+//   - expansion: Template-based step generation
+//   - aspect: Multi-aspect parallel analysis
+//
+// # Quick Start
+//
+// Parse a formula file and get execution order:
+//
+//	f, err := formula.ParseFile("workflow.formula.toml")
+//	if err != nil {
+//	    log.Fatal(err)
+//	}
+//
+//	// Get topologically sorted execution order
+//	order, err := f.TopologicalSort()
+//	if err != nil {
+//	    log.Fatal(err)
+//	}
+//
+//	// Execute steps, tracking completion
+//	completed := make(map[string]bool)
+//	for len(completed) < len(order) {
+//	    ready := f.ReadySteps(completed)
+//	    // Execute ready steps in parallel...
+//	    for _, id := range ready {
+//	        completed[id] = true
+//	    }
+//	}
+//
+// # Formula Types
+//
+// Convoy formulas execute legs in parallel, then synthesize results:
+//
+//	formula = "security-audit"
+//	type = "convoy"
+//
+//	[[legs]]
+//	id = "sast"
+//	title = "Static Analysis"
+//	focus = "Find code vulnerabilities"
+//
+//	[[legs]]
+//	id = "deps"
+//	title = "Dependency Audit"
+//	focus = "Check for vulnerable dependencies"
+//
+//	[synthesis]
+//	title = "Combine Findings"
+//	depends_on = ["sast", "deps"]
+//
+// Workflow formulas execute steps sequentially with dependencies:
+//
+//	formula = "release"
+//	type = "workflow"
+//
+//	[[steps]]
+//	id = "test"
+//	title = "Run Tests"
+//
+//	[[steps]]
+//	id = "build"
+//	title = "Build"
+//	needs = ["test"]
+//
+//	[[steps]]
+//	id = "publish"
+//	title = "Publish"
+//	needs = ["build"]
+//
+// # Validation
+//
+// The package performs comprehensive validation:
+//
+//   - Required fields (formula name, valid type)
+//   - Unique IDs within steps/legs/templates/aspects
+//   - Valid dependency references (needs/depends_on)
+//   - Cycle detection in dependency graphs
+//
+// # Cycle Detection
+//
+// Workflow and expansion formulas are validated for circular dependencies
+// using depth-first search. Cycles are reported with the offending step ID:
+//
+//	f, err := formula.Parse([]byte(tomlContent))
+//	// Returns: "cycle detected involving step: build"
+//
+// # Topological Sorting
+//
+// The TopologicalSort method returns steps in dependency order using
+// Kahn's algorithm. Dependencies are guaranteed to appear before dependents:
+//
+//	order, err := f.TopologicalSort()
+//	// Returns: ["test", "build", "publish"]
+//
+// For convoy and aspect formulas (which are parallel), TopologicalSort
+// returns all items in their original order.
+//
+// # Ready Step Computation
+//
+// The ReadySteps method efficiently computes which steps can execute
+// given a set of completed steps:
+//
+//	completed := map[string]bool{"test": true}
+//	ready := f.ReadySteps(completed)
+//	// Returns: ["build"] (test is done, build can run)
+//
+// # Embedded Formulas
+//
+// The package includes embedded formula files that can be provisioned
+// to a beads workspace. Use ProvisionFormulas for initial setup and
+// UpdateFormulas for safe updates that preserve user modifications.
+//
+// # Thread Safety
+//
+// Formula instances are safe for concurrent read access after parsing.
+// The ReadySteps method does not modify state and can be called from
+// multiple goroutines with different completed maps.
+package formula

internal/formula/example_test.go

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+package formula_test
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/steveyegge/gastown/internal/formula"
+)
+
+func ExampleParse_workflow() {
+	toml := `
+formula = "release"
+description = "Standard release process"
+type = "workflow"
+
+[[steps]]
+id = "test"
+title = "Run Tests"
+
+[[steps]]
+id = "build"
+title = "Build"
+needs = ["test"]
+
+[[steps]]
+id = "publish"
+title = "Publish"
+needs = ["build"]
+`
+	f, err := formula.Parse([]byte(toml))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("Formula: %s\n", f.Name)
+	fmt.Printf("Type: %s\n", f.Type)
+	fmt.Printf("Steps: %d\n", len(f.Steps))
+
+	// Output:
+	// Formula: release
+	// Type: workflow
+	// Steps: 3
+}
+
+func ExampleFormula_TopologicalSort() {
+	toml := `
+formula = "build-pipeline"
+type = "workflow"
+
+[[steps]]
+id = "lint"
+title = "Lint"
+
+[[steps]]
+id = "test"
+title = "Test"
+needs = ["lint"]
+
+[[steps]]
+id = "build"
+title = "Build"
+needs = ["lint"]
+
+[[steps]]
+id = "deploy"
+title = "Deploy"
+needs = ["test", "build"]
+`
+	f, _ := formula.Parse([]byte(toml))
+	order, _ := f.TopologicalSort()
+
+	fmt.Println("Execution order:")
+	for i, id := range order {
+		fmt.Printf("  %d. %s\n", i+1, id)
+	}
+
+	// Output:
+	// Execution order:
+	//   1. lint
+	//   2. test
+	//   3. build
+	//   4. deploy
+}
+
+func ExampleFormula_ReadySteps() {
+	toml := `
+formula = "pipeline"
+type = "workflow"
+
+[[steps]]
+id = "a"
+title = "Step A"
+
+[[steps]]
+id = "b"
+title = "Step B"
+needs = ["a"]
+
+[[steps]]
+id = "c"
+title = "Step C"
+needs = ["a"]
+
+[[steps]]
+id = "d"
+title = "Step D"
+needs = ["b", "c"]
+`
+	f, _ := formula.Parse([]byte(toml))
+
+	// Initially, only "a" is ready (no dependencies)
+	completed := map[string]bool{}
+	ready := f.ReadySteps(completed)
+	fmt.Printf("Initially ready: %v\n", ready)
+
+	// After completing "a", both "b" and "c" become ready
+	completed["a"] = true
+	ready = f.ReadySteps(completed)
+	fmt.Printf("After 'a': %v\n", ready)
+
+	// After completing "b" and "c", "d" becomes ready
+	completed["b"] = true
+	completed["c"] = true
+	ready = f.ReadySteps(completed)
+	fmt.Printf("After 'b' and 'c': %v\n", ready)
+
+	// Output:
+	// Initially ready: [a]
+	// After 'a': [b c]
+	// After 'b' and 'c': [d]
+}
+
+func ExampleParse_convoy() {
+	toml := `
+formula = "security-audit"
+type = "convoy"
+
+[[legs]]
+id = "sast"
+title = "Static Analysis"
+focus = "Code vulnerabilities"
+
+[[legs]]
+id = "deps"
+title = "Dependency Check"
+focus = "Vulnerable packages"
+
+[synthesis]
+title = "Combine Findings"
+depends_on = ["sast", "deps"]
+`
+	f, _ := formula.Parse([]byte(toml))
+
+	fmt.Printf("Formula: %s\n", f.Name)
+	fmt.Printf("Legs: %d\n", len(f.Legs))
+
+	// All legs are ready immediately (parallel execution)
+	ready := f.ReadySteps(map[string]bool{})
+	fmt.Printf("Ready for parallel execution: %v\n", ready)
+
+	// Output:
+	// Formula: security-audit
+	// Legs: 2
+	// Ready for parallel execution: [sast deps]
+}
+
+func ExampleParse_typeInference() {
+	// Type can be inferred from content
+	toml := `
+formula = "auto-typed"
+
+[[steps]]
+id = "first"
+title = "First Step"
+
+[[steps]]
+id = "second"
+title = "Second Step"
+needs = ["first"]
+`
+	f, _ := formula.Parse([]byte(toml))
+
+	// Type was inferred as "workflow" because [[steps]] were present
+	fmt.Printf("Inferred type: %s\n", f.Type)
+
+	// Output:
+	// Inferred type: workflow
+}
+
+func ExampleFormula_Validate_cycleDetection() {
+	// This formula has a cycle: a -> b -> c -> a
+	toml := `
+formula = "cyclic"
+type = "workflow"
+
+[[steps]]
+id = "a"
+title = "Step A"
+needs = ["c"]
+
+[[steps]]
+id = "b"
+title = "Step B"
+needs = ["a"]
+
+[[steps]]
+id = "c"
+title = "Step C"
+needs = ["b"]
+`
+	_, err := formula.Parse([]byte(toml))
+	if err != nil {
+		fmt.Printf("Validation error: %v\n", err)
+	}
+
+	// Output:
+	// Validation error: cycle detected involving step: a
+}
+
+func ExampleFormula_GetStep() {
+	toml := `
+formula = "lookup-demo"
+type = "workflow"
+
+[[steps]]
+id = "build"
+title = "Build Application"
+description = "Compile source code"
+`
+	f, _ := formula.Parse([]byte(toml))
+
+	step := f.GetStep("build")
+	if step != nil {
+		fmt.Printf("Found: %s\n", step.Title)
+		fmt.Printf("Description: %s\n", step.Description)
+	}
+
+	missing := f.GetStep("nonexistent")
+	fmt.Printf("Missing step is nil: %v\n", missing == nil)
+
+	// Output:
+	// Found: Build Application
+	// Description: Compile source code
+	// Missing step is nil: true
+}