feat: add initial helper methods

action.go

@@ -0,0 +1,261 @@
+package sdk
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+const (
+	addMaskCmd = "add-mask"
+
+	envCmd    = "env"
+	outputCmd = "output"
+	pathCmd   = "path"
+	stateCmd  = "state"
+
+	// https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#multiline-strings
+	multiLineFileDelim = "234baa68-d26f-4bf9-996d-45ec3520cb95"
+	multilineFileCmd   = "%s<<" + multiLineFileDelim + "\n%s\n" + multiLineFileDelim // ${name}<<${delimiter}${os.EOL}${convertedVal}${os.EOL}${delimiter}
+
+	addMatcherCmd    = "add-matcher"
+	removeMatcherCmd = "remove-matcher"
+
+	groupCmd    = "group"
+	endGroupCmd = "endgroup"
+
+	stepSummaryCmd = "step-summary"
+
+	debugCmd = "debug"
+
+	noticeCmd  = "notice"
+	warningCmd = "warning"
+	errorCmd   = "error"
+
+	errFileCmdFmt = "unable to write command to the environment file: %s"
+)
+
+type Action struct {
+	w      io.Writer
+	env    func(string) string
+	fields CommandProperties
+}
+
+func New() *Action {
+	return &Action{w: os.Stdout, env: os.Getenv}
+}
+
+// WithFieldsSlice includes the provided fields in log output. "f" must be a
+// slice of k=v pairs. The given slice will be sorted. It panics if any of the
+// string in the given slice does not construct a valid 'key=value' pair.
+func (c *Action) WithFieldsSlice(f ...string) *Action {
+	m := make(CommandProperties)
+	for _, s := range f {
+		pair := strings.SplitN(s, "=", 2)
+		if len(pair) < 2 {
+			panic(fmt.Sprintf("%q is not a proper k=v pair!", s))
+		}
+
+		m[pair[0]] = pair[1]
+	}
+
+	return c.WithFieldsMap(m)
+}
+
+// WithFieldsMap includes the provided fields in log output. The fields in "m"
+// are automatically converted to k=v pairs and sorted.
+func (c *Action) WithFieldsMap(m map[string]string) *Action {
+	return &Action{
+		w:      c.w,
+		fields: m,
+	}
+}
+
+// GetInput gets the input by the given name. It returns the empty string if the
+// input is not defined.
+func (c *Action) GetInput(i string) string {
+	e := strings.ReplaceAll(i, " ", "_")
+	e = strings.ToUpper(e)
+	e = "INPUT_" + e
+	return strings.TrimSpace(c.env(e))
+}
+
+// IssueCommand issues a new GitHub actions Command.
+// It panics if it cannot write to the output stream.
+func (c *Action) IssueCommand(cmd *Command) {
+	if _, err := fmt.Fprintln(c.w, cmd.String()); err != nil {
+		panic(fmt.Errorf("failed to issue command: %w", err))
+	}
+}
+
+// IssueFileCommand issues a new GitHub actions Command using environment files.
+// It panics if writing to the file fails.
+func (c *Action) IssueFileCommand(cmd *Command) {
+	e := strings.ReplaceAll(cmd.Name, "-", "_")
+	e = strings.ToUpper(e)
+	e = "GITHUB_" + e
+
+	filepath := c.env(e)
+	msg := []byte(cmd.Message)
+	f, err := os.OpenFile(filepath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+	if err != nil {
+		panic(fmt.Errorf(errFileCmdFmt, err))
+	}
+
+	defer func() {
+		if err := f.Close(); err != nil {
+			panic(err)
+		}
+	}()
+
+	if _, err := f.Write(msg); err != nil {
+		panic(fmt.Errorf(errFileCmdFmt, err))
+	}
+}
+
+// AddMask adds a new field mask for the given string "p". After called, future
+// attempts to log "p" will be replaced with "***" in log output. It panics if
+// it cannot write to the output stream.
+func (c *Action) AddMask(p string) {
+	// ::add-mask::<p>
+	c.IssueCommand(&Command{
+		Name:    addMaskCmd,
+		Message: p,
+	})
+}
+
+// AddMatcher adds a new matcher with the given file path. It panics if it
+// cannot write to the output stream.
+func (c *Action) AddMatcher(p string) {
+	// ::add-matcher::<p>
+	c.IssueCommand(&Command{
+		Name:    addMatcherCmd,
+		Message: p,
+	})
+}
+
+// RemoveMatcher removes a matcher with the given owner name. It panics if it
+// cannot write to the output stream.
+func (c *Action) RemoveMatcher(o string) {
+	// ::remove-matcher owner=<o>::
+	c.IssueCommand(&Command{
+		Name: removeMatcherCmd,
+		Properties: CommandProperties{
+			"owner": o,
+		},
+	})
+}
+
+// Group starts a new collapsable region up to the next ungroup invocation. It
+// panics if it cannot write to the output stream.
+func (c *Action) Group(t string) {
+	// ::group::<t>
+	c.IssueCommand(&Command{
+		Name:    groupCmd,
+		Message: t,
+	})
+}
+
+// EndGroup ends the current group. It panics if it cannot write to the output
+// stream.
+func (c *Action) EndGroup() {
+	// ::endgroup::
+	c.IssueCommand(&Command{
+		Name: endGroupCmd,
+	})
+}
+
+// Debugf prints a debug-level message. It follows the standard fmt.Printf
+// arguments, appending an OS-specific line break to the end of the message.
+// It panics if it cannot write to the output stream.
+func (c *Action) Debugf(msg string, args ...any) {
+	// ::debug <c.fields>::<msg, args>
+	c.IssueCommand(&Command{
+		Name:       debugCmd,
+		Message:    fmt.Sprintf(msg, args...),
+		Properties: c.fields,
+	})
+}
+
+// Noticef prints a notice-level message. It follows the standard fmt.Printf
+// arguments, appending an OS-specific line break to the end of the message.
+// It panics if it cannot write to the output stream.
+func (c *Action) Noticef(msg string, args ...any) {
+	// ::notice <c.fields>::<msg, args>
+	c.IssueCommand(&Command{
+		Name:       noticeCmd,
+		Message:    fmt.Sprintf(msg, args...),
+		Properties: c.fields,
+	})
+}
+
+// Warningf prints a warning-level message. It follows the standard fmt.Printf
+// arguments, appending an OS-specific line break to the end of the message.
+// It panics if it cannot write to the output stream.
+func (c *Action) Warningf(msg string, args ...any) {
+	// ::warning <c.fields>::<msg, args>
+	c.IssueCommand(&Command{
+		Name:       warningCmd,
+		Message:    fmt.Sprintf(msg, args...),
+		Properties: c.fields,
+	})
+}
+
+// Errorf prints a error-level message. It follows the standard fmt.Printf
+// arguments, appending an OS-specific line break to the end of the message.
+// It panics if it cannot write to the output stream.
+func (c *Action) Errorf(msg string, args ...any) {
+	// ::error <c.fields>::<msg, args>
+	c.IssueCommand(&Command{
+		Name:       errorCmd,
+		Message:    fmt.Sprintf(msg, args...),
+		Properties: c.fields,
+	})
+}
+
+// AddPath adds the string "p" to the path for the invocation.
+// It panics if it cannot write to the output file.
+func (c *Action) AddPath(p string) {
+	c.IssueFileCommand(&Command{
+		Name:    pathCmd,
+		Message: p,
+	})
+}
+
+// SaveState saves state to be used in the "finally" post job entry point.
+// It panics if it cannot write to the output stream.
+func (c *Action) SaveState(k, v string) {
+	c.IssueFileCommand(&Command{
+		Name:    stateCmd,
+		Message: fmt.Sprintf(multilineFileCmd, k, v),
+	})
+}
+
+// AddStepSummary writes the given markdown to the job summary. If a job summary
+// already exists, this value is appended.
+// It panics if it cannot write to the output file.
+func (c *Action) AddStepSummary(markdown string) {
+	c.IssueFileCommand(&Command{
+		Name:    stepSummaryCmd,
+		Message: markdown,
+	})
+}
+
+// SetEnv sets an environment variable.
+// It panics if it cannot write to the output file.
+func (c *Action) SetEnv(k, v string) {
+	c.IssueFileCommand(&Command{
+		Name:    envCmd,
+		Message: fmt.Sprintf(multilineFileCmd, k, v),
+	})
+}
+
+// SetOutput sets an output parameter.
+// It panics if it cannot write to the output file.
+func (c *Action) SetOutput(k, v string) {
+	c.IssueFileCommand(&Command{
+		Name:    outputCmd,
+		Message: fmt.Sprintf(multilineFileCmd, k, v),
+	})
+}

action_test.go

@@ -0,0 +1,443 @@
+package sdk
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"testing"
+)
+
+func newFakeGetenvFunc(t *testing.T, wantKey, v string) func(string) string {
+	return func(gotKey string) string {
+		if gotKey != wantKey {
+			t.Errorf("expected call GetenvFunc(%q) to be GetenvFunc(%q)", gotKey, wantKey)
+		}
+
+		return v
+	}
+}
+
+func TestAction_WithFieldsSlice(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a = a.WithFieldsSlice("line=100", "file=app.js")
+	a.Debugf("fail: %s", "thing")
+
+	if got, want := b.String(), fmt.Sprintln("::debug file=app.js,line=100::fail: thing"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_WithFieldsSlice_Panic(t *testing.T) {
+	t.Parallel()
+
+	defer func() {
+		want := `"no-equals" is not a proper k=v pair!`
+		if got := recover(); got != want {
+			t.Errorf("expected %q to be %q", got, want)
+		}
+	}()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a = a.WithFieldsSlice("no-equals")
+	a.Debugf("fail: %s", "thing")
+}
+
+func TestAction_WithFieldsMap(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a = a.WithFieldsMap(map[string]string{"line": "100", "file": "app.js"})
+	a.Debugf("fail: %s", "thing")
+
+	if got, want := b.String(), fmt.Sprintln("::debug file=app.js,line=100::fail: thing"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_GetInput(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+	a.env = newFakeGetenvFunc(t, "INPUT_FOO", "bar")
+
+	if got, want := a.GetInput("foo"), "bar"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_IssueCommand(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.IssueCommand(&Command{
+		Name:    "foo",
+		Message: "bar",
+	})
+
+	if got, want := b.String(), fmt.Sprintln("::foo::bar"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_IssueFileCommand(t *testing.T) {
+	t.Parallel()
+
+	file, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatalf("unable to create a temp env file: %s", err)
+	}
+	defer os.Remove(file.Name())
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+	a.env = newFakeGetenvFunc(t, "GITHUB_FOO", file.Name())
+
+	a.IssueFileCommand(&Command{
+		Name:    "foo",
+		Message: "bar",
+	})
+
+	// expect an empty stdout buffer
+	if got, want := b.String(), ""; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	// expect the message to be written to the env file
+	data, err := io.ReadAll(file)
+	if err != nil {
+		t.Errorf("unable to read temp env file: %s", err)
+	}
+
+	if got, want := string(data), "bar"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_AddMask(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.AddMask("foobar")
+
+	if got, want := b.String(), fmt.Sprintln("::add-mask::foobar"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_AddMatcher(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.AddMatcher("foobar.json")
+
+	if got, want := b.String(), fmt.Sprintln("::add-matcher::foobar.json"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_RemoveMatcher(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.RemoveMatcher("foobar")
+
+	if got, want := b.String(), fmt.Sprintln("::remove-matcher owner=foobar::"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_Group(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.Group("mygroup")
+
+	if got, want := b.String(), fmt.Sprintln("::group::mygroup"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_EndGroup(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.EndGroup()
+
+	if got, want := b.String(), fmt.Sprintln("::endgroup::"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_Debugf(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.Debugf("fail: %s", "thing")
+
+	if got, want := b.String(), fmt.Sprintln("::debug::fail: thing"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_Noticef(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.Noticef("fail: %s", "thing")
+
+	if got, want := b.String(), fmt.Sprintln("::notice::fail: thing"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_Warningf(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.Warningf("fail: %s", "thing")
+
+	if got, want := b.String(), fmt.Sprintln("::warning::fail: thing"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_Errorf(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+
+	a.Errorf("fail: %s", "thing")
+
+	if got, want := b.String(), fmt.Sprintln("::error::fail: thing"); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_AddPath(t *testing.T) {
+	t.Parallel()
+
+	// expect a file command to be issued when env file is set.
+	file, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatalf("unable to create a temp env file: %s", err)
+	}
+	defer os.Remove(file.Name())
+
+	var b bytes.Buffer
+	a := New()
+	a.w = &b
+	a.env = newFakeGetenvFunc(t, "GITHUB_PATH", file.Name())
+
+	a.AddPath("/custom/bin")
+
+	if got, want := b.String(), ""; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	// expect an empty stdout buffer
+	if got, want := b.String(), ""; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	// expect the message to be written to the file.
+	data, err := io.ReadAll(file)
+	if err != nil {
+		t.Errorf("unable to read temp env file: %s", err)
+	}
+
+	if got, want := string(data), "/custom/bin"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_SaveState(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	file, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatalf("unable to create a temp env file: %s", err)
+	}
+	defer os.Remove(file.Name())
+
+	a := New()
+	a.w = &b
+	a.env = newFakeGetenvFunc(t, "GITHUB_STATE", file.Name())
+
+	a.SaveState("key", "value")
+	a.SaveState("key2", "value2")
+
+	// expect an empty stdout buffer
+	if got, want := b.String(), ""; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	// expect the command to be written to the file.
+	data, err := io.ReadAll(file)
+	if err != nil {
+		t.Errorf("unable to read temp env file: %s", err)
+	}
+
+	want := fmt.Sprintf("key<<%s\nvalue\n%s", multiLineFileDelim, multiLineFileDelim)
+	want += fmt.Sprintf("key2<<%s\nvalue2\n%s", multiLineFileDelim, multiLineFileDelim)
+	if got := string(data); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_AddStepSummary(t *testing.T) {
+	t.Parallel()
+
+	// expectations for env file env commands
+	var b bytes.Buffer
+	file, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatalf("unable to create a temp env file: %s", err)
+	}
+	defer os.Remove(file.Name())
+
+	a := New()
+	a.w = &b
+	a.env = newFakeGetenvFunc(t, "GITHUB_STEP_SUMMARY", file.Name())
+
+	a.AddStepSummary(`
+## This is
+
+some markdown
+`)
+	a.AddStepSummary(`
+- content
+`)
+
+	// expect an empty stdout buffer
+	if got, want := b.String(), ""; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	// expect the command to be written to the file.
+	data, err := io.ReadAll(file)
+	if err != nil {
+		t.Errorf("unable to read temp summary file: %s", err)
+	}
+
+	want := "\n## This is\n\nsome markdown\n\n- content\n"
+	if got := string(data); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_SetEnv(t *testing.T) {
+	t.Parallel()
+
+	// expectations for env file env commands
+	var b bytes.Buffer
+	file, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatalf("unable to create a temp env file: %s", err)
+	}
+	defer os.Remove(file.Name())
+
+	a := New()
+	a.w = &b
+	a.env = newFakeGetenvFunc(t, "GITHUB_ENV", file.Name())
+
+	a.SetEnv("key", "value")
+	a.SetEnv("key2", "value2")
+
+	// expect an empty stdout buffer
+	if got, want := b.String(), ""; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	// expect the command to be written to the file.
+	data, err := io.ReadAll(file)
+	if err != nil {
+		t.Errorf("unable to read temp env file: %s", err)
+	}
+
+	want := fmt.Sprintf("key<<%s\nvalue\n%s", multiLineFileDelim, multiLineFileDelim)
+	want += fmt.Sprintf("key2<<%s\nvalue2\n%s", multiLineFileDelim, multiLineFileDelim)
+	if got := string(data); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestAction_SetOutput(t *testing.T) {
+	t.Parallel()
+
+	// expectations for env file env commands
+	var b bytes.Buffer
+	file, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatalf("unable to create a temp env file: %s", err)
+	}
+	defer os.Remove(file.Name())
+
+	a := New()
+	a.w = &b
+	a.env = newFakeGetenvFunc(t, "GITHUB_OUTPUT", file.Name())
+
+	a.SetOutput("key", "value")
+	a.SetOutput("key2", "value2")
+
+	// expect an empty stdout buffer
+	if got, want := b.String(), ""; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	// expect the command to be written to the file.
+	data, err := io.ReadAll(file)
+	if err != nil {
+		t.Errorf("unable to read temp env file: %s", err)
+	}
+
+	want := fmt.Sprintf("key<<%s\nvalue\n%s", multiLineFileDelim, multiLineFileDelim)
+	want += fmt.Sprintf("key2<<%s\nvalue2\n%s", multiLineFileDelim, multiLineFileDelim)
+	if got := string(data); got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}

command.go

@@ -0,0 +1,83 @@
+package sdk
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+const (
+	cmdSeparator        = "::"
+	cmdPropertiesPrefix = " "
+)
+
+// CommandProperties is a named "map[string]string" type to hold key-value pairs
+// passed to an actions command.
+type CommandProperties map[string]string
+
+// String encodes the CommandProperties to a string as comma separated
+// 'key=value' pairs. The pairs are joined in a chronological order.
+func (props *CommandProperties) String() string {
+	l := make([]string, 0, len(*props))
+	for k, v := range *props {
+		l = append(l, fmt.Sprintf("%s=%s", k, escapeProperty(v)))
+	}
+
+	sort.Strings(l)
+	return strings.Join(l, ",")
+}
+
+// Command can be issued by a GitHub action by writing to `stdout` with
+// following format.
+//
+// ::name key=value,key=value::message
+//
+//	Examples:
+//	  ::warning::This is the message
+//	  ::set-env name=MY_VAR::some value
+type Command struct {
+	Name       string
+	Message    string
+	Properties CommandProperties
+}
+
+// String encodes the Command to a string in the following format:
+//
+// ::name key=value,key=value::message
+func (cmd *Command) String() string {
+	if cmd.Name == "" {
+		cmd.Name = "missing.command"
+	}
+
+	var builder strings.Builder
+	builder.WriteString(cmdSeparator)
+	builder.WriteString(cmd.Name)
+	if len(cmd.Properties) > 0 {
+		builder.WriteString(cmdPropertiesPrefix)
+		builder.WriteString(cmd.Properties.String())
+	}
+
+	builder.WriteString(cmdSeparator)
+	builder.WriteString(escapeData(cmd.Message))
+	return builder.String()
+}
+
+// escapeData escapes string values for presentation in the output of a command.
+// This is a not-so-well-documented requirement of commands that define a message.
+func escapeData(v string) string {
+	v = strings.ReplaceAll(v, "%", "%25")
+	v = strings.ReplaceAll(v, "\r", "%0D")
+	v = strings.ReplaceAll(v, "\n", "%0A")
+	return v
+}
+
+// escapeData escapes command property values for presentation in the output of
+// a command.
+func escapeProperty(v string) string {
+	v = strings.ReplaceAll(v, "%", "%25")
+	v = strings.ReplaceAll(v, "\r", "%0D")
+	v = strings.ReplaceAll(v, "\n", "%0A")
+	v = strings.ReplaceAll(v, ":", "%3A")
+	v = strings.ReplaceAll(v, ",", "%2C")
+	return v
+}

command_test.go

@@ -0,0 +1,45 @@
+package sdk
+
+import "testing"
+
+func TestCommandProperties_String(t *testing.T) {
+	t.Parallel()
+
+	props := CommandProperties{"hello": "world"}
+	if got, want := props.String(), "hello=world"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	props["foo"] = "bar"
+	if got, want := props.String(), "foo=bar,hello=world"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}
+
+func TestCommand_String(t *testing.T) {
+	t.Parallel()
+
+	cmd := Command{Name: "foo"}
+	if got, want := cmd.String(), "::foo::"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	cmd = Command{Name: "foo", Message: "bar"}
+	if got, want := cmd.String(), "::foo::bar"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	cmd = Command{
+		Name:       "foo",
+		Message:    "bar",
+		Properties: CommandProperties{"bar": "foo"},
+	}
+	if got, want := cmd.String(), "::foo bar=foo::bar"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+
+	cmd = Command{Message: "quux"}
+	if got, want := cmd.String(), "::missing.command::quux"; got != want {
+		t.Errorf("expected %q to be %q", got, want)
+	}
+}

context.go

@@ -0,0 +1,189 @@
+package sdk
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+// GitHubContext of current workflow.
+// See: https://docs.github.com/en/actions/learn-github-actions/environment-variables
+type GitHubContext struct {
+	Action           string `env:"GITHUB_ACTION"`
+	ActionPath       string `env:"GITHUB_ACTION_PATH"`
+	ActionRepository string `env:"GITHUB_ACTION_REPOSITORY"`
+	Actions          bool   `env:"GITHUB_ACTIONS"`
+	Actor            string `env:"GITHUB_ACTOR"`
+	APIURL           string `env:"GITHUB_API_URL,default=https://api.github.com"`
+	BaseRef          string `env:"GITHUB_BASE_REF"`
+	Env              string `env:"GITHUB_ENV"`
+	EventName        string `env:"GITHUB_EVENT_NAME"`
+	EventPath        string `env:"GITHUB_EVENT_PATH"`
+	GraphqlURL       string `env:"GITHUB_GRAPHQL_URL,default=https://api.github.com/graphql"`
+	HeadRef          string `env:"GITHUB_HEAD_REF"`
+	Job              string `env:"GITHUB_JOB"`
+	Path             string `env:"GITHUB_PATH"`
+	Ref              string `env:"GITHUB_REF"`
+	RefName          string `env:"GITHUB_REF_NAME"`
+	RefProtected     bool   `env:"GITHUB_REF_PROTECTED"`
+	RefType          string `env:"GITHUB_REF_TYPE"`
+
+	Repository      string `env:"GITHUB_REPOSITORY"`
+	RepositoryOwner string `env:"GITHUB_REPOSITORY_OWNER"`
+
+	RetentionDays int64  `env:"GITHUB_RETENTION_DAYS"`
+	RunAttempt    int64  `env:"GITHUB_RUN_ATTEMPT"`
+	RunID         int64  `env:"GITHUB_RUN_ID"`
+	RunNumber     int64  `env:"GITHUB_RUN_NUMBER"`
+	ServerURL     string `env:"GITHUB_SERVER_URL,default=https://github.com"`
+	SHA           string `env:"GITHUB_SHA"`
+	StepSummary   string `env:"GITHUB_STEP_SUMMARY"`
+	Workflow      string `env:"GITHUB_WORKFLOW"`
+	Workspace     string `env:"GITHUB_WORKSPACE"`
+
+	// Event is populated by parsing the file at EventPath, if it exists.
+	Event map[string]any
+}
+
+// Context returns the context of current action with the payload object
+// that triggered the workflow
+func (c *Action) Context() (*GitHubContext, error) {
+	var merr error
+	context := &GitHubContext{
+		APIURL:     "https://api.github.com",
+		GraphqlURL: "https://api.github.com/graphql",
+		ServerURL:  "https://github.com",
+	}
+
+	if v := c.env("GITHUB_ACTION"); v != "" {
+		context.Action = v
+	}
+	if v := c.env("GITHUB_ACTION_PATH"); v != "" {
+		context.ActionPath = v
+	}
+	if v := c.env("GITHUB_ACTION_REPOSITORY"); v != "" {
+		context.ActionRepository = v
+	}
+	if v, err := parseBool(c.env("GITHUB_ACTIONS")); err == nil {
+		context.Actions = v
+	} else {
+		merr = errors.Join(merr, err)
+	}
+	if v := c.env("GITHUB_ACTOR"); v != "" {
+		context.Actor = v
+	}
+	if v := c.env("GITHUB_API_URL"); v != "" {
+		context.APIURL = v
+	}
+	if v := c.env("GITHUB_BASE_REF"); v != "" {
+		context.BaseRef = v
+	}
+	if v := c.env("GITHUB_ENV"); v != "" {
+		context.Env = v
+	}
+	if v := c.env("GITHUB_EVENT_NAME"); v != "" {
+		context.EventName = v
+	}
+	if v := c.env("GITHUB_EVENT_PATH"); v != "" {
+		context.EventPath = v
+	}
+	if v := c.env("GITHUB_GRAPHQL_URL"); v != "" {
+		context.GraphqlURL = v
+	}
+	if v := c.env("GITHUB_HEAD_REF"); v != "" {
+		context.HeadRef = v
+	}
+	if v := c.env("GITHUB_JOB"); v != "" {
+		context.Job = v
+	}
+	if v := c.env("GITHUB_PATH"); v != "" {
+		context.Path = v
+	}
+	if v := c.env("GITHUB_REF"); v != "" {
+		context.Ref = v
+	}
+	if v := c.env("GITHUB_REF_NAME"); v != "" {
+		context.RefName = v
+	}
+	if v, err := parseBool(c.env("GITHUB_REF_PROTECTED")); err == nil {
+		context.RefProtected = v
+	} else {
+		merr = errors.Join(merr, err)
+	}
+	if v := c.env("GITHUB_REF_TYPE"); v != "" {
+		context.RefType = v
+	}
+
+	if v := c.env("GITHUB_REPOSITORY"); v != "" {
+		context.Repository = v
+	}
+	if v := c.env("GITHUB_REPOSITORY_OWNER"); v != "" {
+		context.RepositoryOwner = v
+	}
+
+	if v, err := parseInt(c.env("GITHUB_RETENTION_DAYS")); err == nil {
+		context.RetentionDays = v
+	} else {
+		merr = errors.Join(merr, err)
+	}
+	if v, err := parseInt(c.env("GITHUB_RUN_ATTEMPT")); err == nil {
+		context.RunAttempt = v
+	} else {
+		merr = errors.Join(merr, err)
+	}
+	if v, err := parseInt(c.env("GITHUB_RUN_ID")); err == nil {
+		context.RunID = v
+	} else {
+		merr = errors.Join(merr, err)
+	}
+	if v, err := parseInt(c.env("GITHUB_RUN_NUMBER")); err == nil {
+		context.RunNumber = v
+	} else {
+		merr = errors.Join(merr, err)
+	}
+	if v := c.env("GITHUB_SERVER_URL"); v != "" {
+		context.ServerURL = v
+	}
+	if v := c.env("GITHUB_SHA"); v != "" {
+		context.SHA = v
+	}
+	if v := c.env("GITHUB_STEP_SUMMARY"); v != "" {
+		context.StepSummary = v
+	}
+	if v := c.env("GITHUB_WORKFLOW"); v != "" {
+		context.Workflow = v
+	}
+	if v := c.env("GITHUB_WORKSPACE"); v != "" {
+		context.Workspace = v
+	}
+
+	if context.EventPath != "" {
+		eventData, err := os.ReadFile(context.EventPath)
+		if err != nil && !os.IsNotExist(err) {
+			return nil, fmt.Errorf("could not read event file: %w", err)
+		}
+		if eventData != nil {
+			if err := json.Unmarshal(eventData, &context.Event); err != nil {
+				return nil, fmt.Errorf("failed to unmarshal event payload: %w", err)
+			}
+		}
+	}
+
+	return context, merr
+}
+
+func parseBool(v string) (bool, error) {
+	if v == "" {
+		return false, nil
+	}
+	return strconv.ParseBool(v)
+}
+
+func parseInt(v string) (int64, error) {
+	if v == "" {
+		return 0, nil
+	}
+	return strconv.ParseInt(v, 10, 64)
+}

context_test.go

@@ -0,0 +1,144 @@
+package sdk
+
+import (
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestAction_Context(t *testing.T) {
+	t.Parallel()
+
+	f, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { os.Remove(f.Name()) })
+
+	if _, err := f.Write([]byte(`{"foo": "bar"}`)); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	eventPayloadPath := f.Name()
+
+	cases := []struct {
+		name string
+		env  map[string]string
+		exp  *GitHubContext
+	}{
+		{
+			name: "empty",
+			env:  nil,
+			exp: &GitHubContext{
+				// Defaults
+				APIURL:     "https://api.github.com",
+				ServerURL:  "https://github.com",
+				GraphqlURL: "https://api.github.com/graphql",
+			},
+		},
+		{
+			name: "no_payload",
+			env: map[string]string{
+				"GITHUB_ACTION":            "__repo-owner_name-of-action-repo",
+				"GITHUB_ACTION_PATH":       "/path/to/action",
+				"GITHUB_ACTION_REPOSITORY": "repo-owner/name-of-action-repo",
+				"GITHUB_ACTIONS":           "true",
+				"GITHUB_ACTOR":             "sethvargo",
+				"GITHUB_API_URL":           "https://foo.com",
+				"GITHUB_BASE_REF":          "main",
+				"GITHUB_ENV":               "/path/to/env",
+				"GITHUB_EVENT_NAME":        "event_name",
+				"GITHUB_HEAD_REF":          "headbranch",
+				"GITHUB_GRAPHQL_URL":       "https://baz.com",
+				"GITHUB_JOB":               "12",
+				"GITHUB_PATH":              "/path/to/path",
+				"GITHUB_REF":               "refs/tags/v1.0",
+				"GITHUB_REF_NAME":          "v1.0",
+				"GITHUB_REF_PROTECTED":     "true",
+				"GITHUB_REF_TYPE":          "tag",
+				"GITHUB_REPOSITORY":        "sethvargo/baz",
+				"GITHUB_REPOSITORY_OWNER":  "sethvargo",
+				"GITHUB_RETENTION_DAYS":    "90",
+				"GITHUB_RUN_ATTEMPT":       "6",
+				"GITHUB_RUN_ID":            "56",
+				"GITHUB_RUN_NUMBER":        "34",
+				"GITHUB_SERVER_URL":        "https://bar.com",
+				"GITHUB_SHA":               "abcd1234",
+				"GITHUB_STEP_SUMMARY":      "/path/to/summary",
+				"GITHUB_WORKFLOW":          "test",
+				"GITHUB_WORKSPACE":         "/path/to/workspace",
+			},
+			exp: &GitHubContext{
+				Action:           "__repo-owner_name-of-action-repo",
+				ActionPath:       "/path/to/action",
+				ActionRepository: "repo-owner/name-of-action-repo",
+				Actions:          true,
+				Actor:            "sethvargo",
+				APIURL:           "https://foo.com",
+				BaseRef:          "main",
+				Env:              "/path/to/env",
+				EventName:        "event_name",
+				// NOTE: No EventPath
+				GraphqlURL:      "https://baz.com",
+				Job:             "12",
+				HeadRef:         "headbranch",
+				Path:            "/path/to/path",
+				Ref:             "refs/tags/v1.0",
+				RefName:         "v1.0",
+				RefProtected:    true,
+				RefType:         "tag",
+				Repository:      "sethvargo/baz",
+				RepositoryOwner: "sethvargo",
+				RetentionDays:   90,
+				RunAttempt:      6,
+				RunID:           56,
+				RunNumber:       34,
+				ServerURL:       "https://bar.com",
+				SHA:             "abcd1234",
+				StepSummary:     "/path/to/summary",
+				Workflow:        "test",
+				Workspace:       "/path/to/workspace",
+			},
+		},
+		{
+			name: "payload",
+			env: map[string]string{
+				"GITHUB_EVENT_PATH": eventPayloadPath,
+			},
+			exp: &GitHubContext{
+				EventPath: eventPayloadPath,
+
+				// Defaults
+				APIURL:     "https://api.github.com",
+				ServerURL:  "https://github.com",
+				GraphqlURL: "https://api.github.com/graphql",
+
+				Event: map[string]any{
+					"foo": "bar",
+				},
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		tc := tc
+
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			a := New()
+			a.env = func(s string) string { return tc.env[s] }
+			got, err := a.Context()
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !reflect.DeepEqual(got, tc.exp) {
+				t.Errorf("expected\n\n%#v\n\nto be\n\n%#v\n", got, tc.exp)
+			}
+		})
+	}
+}