feat(setup): add an OpenCode adapter for the setup agent (1/6)

internal/setup/agent/agent.go

@@ -0,0 +1,168 @@
+// Package agent runs the setup agent: an OpenCode session that adds LaunchDarkly
+// SDK initialization code to the user's project.
+//
+// The CLI owns the OpenCode process. It starts OpenCode in the project
+// directory, sends one task, turns the session events into Events, and stops
+// OpenCode when the run ends. OpenCode edits the files. The CLI never gives
+// OpenCode a LaunchDarkly credential.
+package agent
+
+import "context"
+
+// Task describes the project and what the agent must do in it.
+type Task struct {
+	// Dir is the project directory that OpenCode edits.
+	Dir            string
+	SDKID          string
+	Language       string
+	Framework      string
+	EntryPoint     string
+	PackageManager string
+	// FlagKey is the flag that the new code evaluates.
+	FlagKey string
+	// SDKInstalled reports that the install step added the SDK package, so the
+	// agent does not need to install it.
+	SDKInstalled bool
+}
+
+// Config is how the agent behaves for one run: the model and the instructions.
+type Config struct {
+	// ProviderID and ModelID select the OpenCode model. If both are empty,
+	// OpenCode uses its own default model.
+	ProviderID   string
+	ModelID      string
+	Instructions string
+}
+
+// ConfigSource gives the agent configuration for a task.
+//
+// The setup-agent AI Config will be the source when the Go AI SDK has an
+// OpenCode handler. Until then, DefaultConfigSource supplies built-in
+// instructions.
+type ConfigSource interface {
+	Resolve(ctx context.Context, task Task) (Config, error)
+}
+
+// DefaultConfigSource returns the built-in instructions and no model, so
+// OpenCode uses the model that the user configured for it.
+type DefaultConfigSource struct{}
+
+func (DefaultConfigSource) Resolve(context.Context, Task) (Config, error) {
+	return Config{Instructions: DefaultInstructions}, nil
+}
+
+// EventKind identifies what an Event reports.
+type EventKind int
+
+const (
+	// EventText carries a part of the assistant's reply in Text.
+	EventText EventKind = iota
+	// EventTool reports a tool call that started, finished, or failed.
+	EventTool
+	// EventPermission asks the user to allow or reject a tool call.
+	EventPermission
+	// EventQuestion asks the user to choose an option for each question in
+	// Question.
+	EventQuestion
+	// EventFileEdited reports a file that OpenCode changed, in File.
+	EventFileEdited
+	// EventUsage reports the model and the tokens of one finished reply.
+	EventUsage
+	// EventDone reports that the session finished. It is the last event.
+	EventDone
+	// EventError reports that the run failed, with the reason in Text. It is
+	// the last event.
+	EventError
+)
+
+// Event is one thing that happened in the agent run.
+type Event struct {
+	Kind       EventKind
+	Text       string
+	Tool       ToolCall
+	Permission PermissionRequest
+	Question   QuestionRequest
+	File       string
+	Usage      Usage
+}
+
+// ToolCall is the state of one tool call.
+type ToolCall struct {
+	ID string
+	// Name is the tool, for example "edit" or "bash".
+	Name string
+	// Status is "running", "completed", or "error".
+	Status string
+	// Title is OpenCode's short description of the call, if it has one.
+	Title string
+}
+
+// PermissionRequest is a tool call that waits for the user's answer.
+type PermissionRequest struct {
+	ID        string
+	SessionID string
+	// Permission is the permission type, for example "bash" or "edit".
+	Permission string
+	// Patterns are what the call applies to, for example the command to run.
+	Patterns []string
+	// legacy marks a request from an OpenCode version that uses the
+	// session-scoped reply endpoint.
+	legacy bool
+}
+
+// QuestionRequest is a set of questions from the agent that waits for the
+// user's answers. The agent asks with OpenCode's question tool.
+type QuestionRequest struct {
+	ID        string
+	SessionID string
+	Questions []Question
+}
+
+// Question is one question with its choices.
+type Question struct {
+	// Header is a short label, at most 30 characters.
+	Header  string
+	Text    string
+	Options []QuestionOption
+	// Multiple reports that the user can choose more than one option.
+	Multiple bool
+}
+
+// QuestionOption is one choice for a question.
+type QuestionOption struct {
+	Label       string
+	Description string
+}
+
+// Usage is the model and the token counts of one finished reply.
+type Usage struct {
+	ProviderID   string
+	ModelID      string
+	InputTokens  int
+	OutputTokens int
+	Cost         float64
+}
+
+// Runner starts agent runs.
+type Runner interface {
+	// Check returns an error that tells the user why the agent cannot run, or
+	// nil if it can.
+	Check(ctx context.Context) error
+	// Start begins a run for the task. The caller must Close the run.
+	Start(ctx context.Context, task Task) (Run, error)
+}
+
+// Run is one agent run in progress.
+type Run interface {
+	// Events delivers the run's events. The channel closes after EventDone or
+	// EventError.
+	Events() <-chan Event
+	// Reply answers a permission request.
+	Reply(ctx context.Context, req PermissionRequest, allow bool) error
+	// Answer replies to a question request with the chosen option labels, one
+	// list for each question, in order. A nil answers value dismisses the
+	// questions, and the agent continues without answers.
+	Answer(ctx context.Context, req QuestionRequest, answers [][]string) error
+	// Close stops OpenCode. It is safe to call more than once.
+	Close() error
+}