feat: hook payload marshal/unmarshal helpers

This commit is contained in:
2026-04-07 00:37:40 +02:00
parent ff9fd8c294
commit 345fa5bbd4
2 changed files with 383 additions and 0 deletions

152
internal/hook/payload.go Normal file
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@@ -0,0 +1,152 @@
package hook
import (
"encoding/json"
"fmt"
)
// MarshalPreToolPayload builds the stdin payload for a PreToolUse hook.
func MarshalPreToolPayload(tool string, args json.RawMessage) []byte {
b, _ := json.Marshal(map[string]any{
"event": "pre_tool_use",
"tool": tool,
"args": args,
})
return b
}
// MarshalPostToolPayload builds the stdin payload for a PostToolUse hook.
func MarshalPostToolPayload(tool string, args json.RawMessage, output string, metadata map[string]any) []byte {
b, _ := json.Marshal(map[string]any{
"event": "post_tool_use",
"tool": tool,
"args": args,
"result": map[string]any{
"output": output,
"metadata": metadata,
},
})
return b
}
// MarshalSessionStartPayload builds the stdin payload for a SessionStart hook.
func MarshalSessionStartPayload(sessionID, mode string) []byte {
b, _ := json.Marshal(map[string]any{
"event": "session_start",
"session_id": sessionID,
"mode": mode,
})
return b
}
// MarshalSessionEndPayload builds the stdin payload for a SessionEnd hook.
func MarshalSessionEndPayload(sessionID string, turns int) []byte {
b, _ := json.Marshal(map[string]any{
"event": "session_end",
"session_id": sessionID,
"turns": turns,
})
return b
}
// MarshalPreCompactPayload builds the stdin payload for a PreCompact hook.
func MarshalPreCompactPayload(messageCount, tokenEstimate int) []byte {
b, _ := json.Marshal(map[string]any{
"event": "pre_compact",
"message_count": messageCount,
"token_estimate": tokenEstimate,
})
return b
}
// MarshalStopPayload builds the stdin payload for a Stop hook.
func MarshalStopPayload(reason string) []byte {
b, _ := json.Marshal(map[string]any{
"event": "stop",
"reason": reason,
})
return b
}
// ExtractToolName extracts the "tool" field from a hook payload.
// Returns "" for non-tool events or malformed payloads.
func ExtractToolName(payload []byte) string {
var v struct {
Tool string `json:"tool"`
}
if err := json.Unmarshal(payload, &v); err != nil {
return ""
}
return v.Tool
}
// hookOutput is the JSON structure a hook may write to stdout.
type hookOutput struct {
Action string `json:"action"`
Transformed json.RawMessage `json:"transformed"`
}
// ParseHookOutput parses hook stdout and exit code into an Action and optional
// transformed payload. JSON "action" field overrides the exit code when present.
// Empty stdout falls back to exit code alone.
func ParseHookOutput(stdout []byte, exitCode int) (Action, json.RawMessage, error) {
if len(stdout) == 0 {
action, err := ParseAction(exitCode)
return action, nil, err
}
var out hookOutput
if err := json.Unmarshal(stdout, &out); err != nil {
return 0, nil, fmt.Errorf("hook: invalid stdout JSON: %w", err)
}
var action Action
if out.Action != "" {
var err error
action, err = parseActionString(out.Action)
if err != nil {
return 0, nil, err
}
} else {
var err error
action, err = ParseAction(exitCode)
if err != nil {
return 0, nil, err
}
}
var transformed json.RawMessage
if len(out.Transformed) > 0 {
transformed = out.Transformed
}
return action, transformed, nil
}
// parseActionString maps a JSON "action" string to an Action.
func parseActionString(s string) (Action, error) {
switch s {
case "allow":
return Allow, nil
case "deny":
return Deny, nil
case "skip":
return Skip, nil
default:
return 0, fmt.Errorf("hook: unknown action string %q", s)
}
}
// ExtractTransformedOutput extracts the "output" string from a PostToolUse
// transformed payload. Returns "" if the payload is nil or malformed.
func ExtractTransformedOutput(transformed json.RawMessage) string {
if transformed == nil {
return ""
}
var v struct {
Output string `json:"output"`
}
if err := json.Unmarshal(transformed, &v); err != nil {
return ""
}
return v.Output
}

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@@ -0,0 +1,231 @@
package hook
import (
"encoding/json"
"testing"
)
func TestMarshalPreToolPayload(t *testing.T) {
args := json.RawMessage(`{"command":"ls -la"}`)
payload := MarshalPreToolPayload("bash", args)
var got map[string]any
if err := json.Unmarshal(payload, &got); err != nil {
t.Fatalf("invalid JSON: %v", err)
}
if got["event"] != "pre_tool_use" {
t.Errorf("event = %q, want %q", got["event"], "pre_tool_use")
}
if got["tool"] != "bash" {
t.Errorf("tool = %q, want %q", got["tool"], "bash")
}
if got["args"] == nil {
t.Error("args field missing")
}
}
func TestMarshalPostToolPayload(t *testing.T) {
args := json.RawMessage(`{"command":"ls"}`)
payload := MarshalPostToolPayload("bash", args, "file1\nfile2", nil)
var got map[string]any
if err := json.Unmarshal(payload, &got); err != nil {
t.Fatalf("invalid JSON: %v", err)
}
if got["event"] != "post_tool_use" {
t.Errorf("event = %q, want %q", got["event"], "post_tool_use")
}
if got["tool"] != "bash" {
t.Errorf("tool = %q, want %q", got["tool"], "bash")
}
result, ok := got["result"].(map[string]any)
if !ok {
t.Fatal("result field missing or wrong type")
}
if result["output"] != "file1\nfile2" {
t.Errorf("result.output = %q, want %q", result["output"], "file1\nfile2")
}
}
func TestMarshalSessionStartPayload(t *testing.T) {
payload := MarshalSessionStartPayload("abc-123", "tui")
var got map[string]any
if err := json.Unmarshal(payload, &got); err != nil {
t.Fatalf("invalid JSON: %v", err)
}
if got["event"] != "session_start" {
t.Errorf("event = %q, want %q", got["event"], "session_start")
}
if got["session_id"] != "abc-123" {
t.Errorf("session_id = %q, want %q", got["session_id"], "abc-123")
}
if got["mode"] != "tui" {
t.Errorf("mode = %q, want %q", got["mode"], "tui")
}
}
func TestMarshalSessionEndPayload(t *testing.T) {
payload := MarshalSessionEndPayload("abc-123", 42)
var got map[string]any
if err := json.Unmarshal(payload, &got); err != nil {
t.Fatalf("invalid JSON: %v", err)
}
if got["event"] != "session_end" {
t.Errorf("event = %q, want %q", got["event"], "session_end")
}
if got["session_id"] != "abc-123" {
t.Errorf("session_id = %q, want %q", got["session_id"], "abc-123")
}
if int(got["turns"].(float64)) != 42 {
t.Errorf("turns = %v, want 42", got["turns"])
}
}
func TestMarshalPreCompactPayload(t *testing.T) {
payload := MarshalPreCompactPayload(87, 120000)
var got map[string]any
if err := json.Unmarshal(payload, &got); err != nil {
t.Fatalf("invalid JSON: %v", err)
}
if got["event"] != "pre_compact" {
t.Errorf("event = %q, want %q", got["event"], "pre_compact")
}
if int(got["message_count"].(float64)) != 87 {
t.Errorf("message_count = %v, want 87", got["message_count"])
}
if int(got["token_estimate"].(float64)) != 120000 {
t.Errorf("token_estimate = %v, want 120000", got["token_estimate"])
}
}
func TestMarshalStopPayload(t *testing.T) {
payload := MarshalStopPayload("max_turns")
var got map[string]any
if err := json.Unmarshal(payload, &got); err != nil {
t.Fatalf("invalid JSON: %v", err)
}
if got["event"] != "stop" {
t.Errorf("event = %q, want %q", got["event"], "stop")
}
if got["reason"] != "max_turns" {
t.Errorf("reason = %q, want %q", got["reason"], "max_turns")
}
}
func TestExtractToolName(t *testing.T) {
tests := []struct {
name string
payload []byte
want string
}{
{
"pre_tool_use payload",
[]byte(`{"event":"pre_tool_use","tool":"bash","args":{}}`),
"bash",
},
{
"post_tool_use payload",
[]byte(`{"event":"post_tool_use","tool":"fs.read","args":{}}`),
"fs.read",
},
{
"session_start has no tool",
[]byte(`{"event":"session_start","session_id":"x","mode":"tui"}`),
"",
},
{
"empty payload",
[]byte(`{}`),
"",
},
{
"malformed JSON",
[]byte(`not json`),
"",
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
if got := ExtractToolName(tt.payload); got != tt.want {
t.Errorf("ExtractToolName() = %q, want %q", got, tt.want)
}
})
}
}
func TestParseHookOutput_JSONActionOverridesExitCode(t *testing.T) {
// stdout says deny, exit code 0 — JSON wins
stdout := []byte(`{"action":"deny","transformed":{"command":"safe"}}`)
action, transformed, err := ParseHookOutput(stdout, 0)
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
if action != Deny {
t.Errorf("action = %v, want Deny", action)
}
if transformed == nil {
t.Error("transformed should not be nil")
}
}
func TestParseHookOutput_EmptyStdoutFallsBackToExitCode(t *testing.T) {
tests := []struct {
exitCode int
want Action
}{
{0, Allow},
{1, Skip},
{2, Deny},
}
for _, tt := range tests {
action, transformed, err := ParseHookOutput(nil, tt.exitCode)
if err != nil {
t.Errorf("exit %d: unexpected error: %v", tt.exitCode, err)
continue
}
if action != tt.want {
t.Errorf("exit %d: action = %v, want %v", tt.exitCode, action, tt.want)
}
if transformed != nil {
t.Errorf("exit %d: expected nil transformed", tt.exitCode)
}
}
}
func TestParseHookOutput_MalformedJSON(t *testing.T) {
// non-empty stdout that isn't valid JSON falls back to exit code
_, _, err := ParseHookOutput([]byte("not json"), 0)
if err == nil {
t.Error("expected error for malformed JSON stdout")
}
}
func TestParseHookOutput_AllowString(t *testing.T) {
stdout := []byte(`{"action":"allow"}`)
action, _, err := ParseHookOutput(stdout, 2) // exit 2 but JSON says allow
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
if action != Allow {
t.Errorf("action = %v, want Allow", action)
}
}
func TestExtractTransformedOutput(t *testing.T) {
transformed := json.RawMessage(`{"output":"rewritten result","metadata":{"key":"val"}}`)
got := ExtractTransformedOutput(transformed)
if got != "rewritten result" {
t.Errorf("ExtractTransformedOutput() = %q, want %q", got, "rewritten result")
}
}
func TestExtractTransformedOutput_Empty(t *testing.T) {
got := ExtractTransformedOutput(nil)
if got != "" {
t.Errorf("ExtractTransformedOutput(nil) = %q, want %q", got, "")
}
}