Skill: Goca Architecture

Domain: Understanding the internal architecture of the Goca CLI code generator — how commands, templates, validators, and subsystems interact.

How a Goca Command Works (End-to-End)

When a user runs goca entity Product --fields "Name:string":

cobra.Command.Run()
    ↓
1. Flag parsing (cobra flags → local vars)
    ↓
2. ConfigIntegration.LoadConfigForProject() — reads .goca.yaml
   ConfigIntegration.MergeWithCLIFlags()    — CLI overrides config
    ↓
3. SafetyManager = NewSafetyManager(dryRun, force, backup)
    ↓
4. CommandValidator.ValidateEntityName(name) — rejects invalid names
   FieldValidator.ParseFields(fieldsStr)    — parses "Name:string,Price:float64"
    ↓
5. TemplateGenerator.BuildTemplateData()    — populates TemplateData struct
    ↓
6. TemplateGenerator.GenerateFromTemplate() — text/template rendering
    ↓
7. SafetyManager.WriteFile(path, content)   — writes with conflict checking
    ↓
8. DependencyManager.AddDependency()        — queues go.mod updates
   DependencyManager.RunGoGet()             — executes go get
    ↓
9. Print summary (files created, dry-run preview, etc.)

Key Subsystem Details

TemplateData Struct

The central data structure passed to all templates:

type TemplateData struct {
    Entity   EntityData    // Name, NameLower, NamePlural, Package
    Fields   []FieldData   // Name, Type, JSONTag, GormTag, ValidateTag, flags
    Module   string        // go module path (e.g. "github.com/user/project")
    Database string        // "postgres", "mysql", "sqlite", etc.
    Features FeatureFlags  // Validation, BusinessRules, Timestamps, SoftDelete, etc.
    Imports  []string      // deduplicated import paths for the generated file
    Methods  []MethodData  // (for use case / handler templates)
}

All template variables MUST reference TemplateData fields — never hardcoded strings.

SafetyManager Flow

WriteFile(path, content)
    → CheckFileConflict(path)
        → if file exists AND !Force → error
        → if file exists AND Backup → BackupFile(path)
        → if DryRun → record to createdFiles, return nil (no write)
    → os.MkdirAll(dir, 0755)
    → os.WriteFile(path, []byte(content), 0644)
    → append to createdFiles

ConfigIntegration Priority

Config is resolved in this priority order (highest first):

1. CLI flags explicitly set by user (--database postgres)
2. .goca.yaml configuration file values
3. Built-in defaults (e.g., database: sqlite)

FieldValidator Type Support

Supports all standard Go types plus complex ones:

• Basic: string, int, int64, float64, bool, uint, byte, rune
• Pointers: *string, *User
• Slices: []string, []*User, [][]string
• Arrays: [10]string
• Maps: map[string]string, map[string]interface{}
• Channels: chan string, <-chan int, chan<- bool
• Functions: func(), func(string) error
• Interfaces: interface{}, io.Reader
• Qualified: time.Time, uuid.UUID

Invalid map keys (not comparable): map[[]string]int, map[func()]string

Database Backend Matrix

Goca supports 8 database backends. Repository templates vary by database:

MongoDB, Redis, Cassandra, and DynamoDB use non-GORM templates — they have separate template functions.

Handler Protocol Matrix

Template String Organization

cmd/templates.go              ← entity, usecase, repository, handler templates
cmd/template_components.go    ← reusable partial templates (field blocks, import blocks)
cmd/project_templates.go      ← goca init project structure templates (main.go, go.mod, etc.)

Error Types (cmd/errors.go)

Typed errors for clean error handling:

• ErrInvalidEntityName — name fails regex validation
• ErrInvalidFieldType — field type not supported
• ErrInvalidDatabase — unknown database backend
• ErrFileConflict — file already exists (use --force)
• ErrTemplateRender — template execution failed
• ErrDependencyInstall — go get failed

Integration Test Architecture

internal/testing/tests/
├── entity_test.go      Tests goca entity command end-to-end
├── feature_test.go     Tests goca feature command (all layers)
├── usecase_test.go     Tests goca usecase command
├── handler_test.go     Tests goca handler command
├── init_test.go        Tests goca init command (project scaffold)
└── safety_test.go      Tests SafetyManager, NameConflictDetector, DependencyManager

Each test:

1. Creates t.TempDir() as project root
2. Initializes a Go module with go mod init <test-module>
3. Runs the command targeting that directory
4. Verifies expected files exist
5. Runs go build ./... and go vet ./... to confirm validity