package resource

import (
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strings"
	"testing"

	"github.com/hashicorp/terraform/config"
	"github.com/hashicorp/terraform/terraform"
)

const TestEnvVar = "TF_ACC"

// TestCheckFunc is the callback type used with acceptance tests to check
// the state of a resource. The state passed in is the latest state known,
// or in the case of being after a destroy, it is the last known state when
// it was created.
type TestCheckFunc func(*terraform.State) error

// TestCase is a single acceptance test case used to test the apply/destroy
// lifecycle of a resource in a specific configuration.
type TestCase struct {
	// Provider is the ResourceProvider that will be under test.
	Providers map[string]terraform.ResourceProvider

	// CheckDestroy is called after the resource is finally destroyed
	// to allow the tester to test that the resource is truly gone.
	CheckDestroy TestCheckFunc

	// Steps are the apply sequences done within the context of the
	// same state. Each step can have its own check to verify correctness.
	Steps []TestStep
}

// TestStep is a single apply sequence of a test, done within the
// context of a state.
//
// Multiple TestSteps can be sequenced in a Test to allow testing
// potentially complex update logic. In general, simply create/destroy
// tests will only need one step.
type TestStep struct {
	// Config a string of the configuration to give to Terraform.
	Config string

	// Check is called after the Config is applied. Use this step to
	// make your own API calls to check the status of things, and to
	// inspect the format of the ResourceState itself.
	//
	// If an error is returned, the test will fail. In this case, a
	// destroy plan will still be attempted.
	//
	// If this is nil, no check is done on this step.
	Check TestCheckFunc

	// Destroy will create a destroy plan if set to true.
	Destroy bool
}

// Test performs an acceptance test on a resource.
//
// Tests are not run unless an environmental variable "TF_ACC" is
// set to some non-empty value. This is to avoid test cases surprising
// a user by creating real resources.
//
// Tests will fail unless the verbose flag (`go test -v`, or explicitly
// the "-test.v" flag) is set. Because some acceptance tests take quite
// long, we require the verbose flag so users are able to see progress
// output.
func Test(t TestT, c TestCase) {
	// We only run acceptance tests if an env var is set because they're
	// slow and generally require some outside configuration.
	if os.Getenv(TestEnvVar) == "" {
		t.Skip(fmt.Sprintf(
			"Acceptance tests skipped unless env '%s' set",
			TestEnvVar))
		return
	}

	// We require verbose mode so that the user knows what is going on.
	if !testTesting && !testing.Verbose() {
		t.Fatal("Acceptance tests must be run with the -v flag on tests")
		return
	}

	// Build our context options that we can
	ctxProviders := make(map[string]terraform.ResourceProviderFactory)
	for k, p := range c.Providers {
		ctxProviders[k] = terraform.ResourceProviderFactoryFixed(p)
	}
	opts := terraform.ContextOpts{Providers: ctxProviders}

	// A single state variable to track the lifecycle, starting with no state
	var state *terraform.State

	// Go through each step and run it
	for i, step := range c.Steps {
		var err error
		state, err = testStep(opts, state, step)
		if err != nil {
			t.Error(fmt.Sprintf(
				"Step %d error: %s", i, err))
			break
		}
	}

	// If we have a state, then run the destroy
	if state != nil {
		destroyStep := TestStep{
			Config:  c.Steps[len(c.Steps)-1].Config,
			Check:   c.CheckDestroy,
			Destroy: true,
		}

		state, err := testStep(opts, state, destroyStep)
		if err != nil {
			t.Error(fmt.Sprintf(
				"Error destroying resource! WARNING: Dangling resources\n"+
					"may exist. The full state and error is shown below.\n\n"+
					"Error: %s\n\nState: %s",
				err,
				state))
		}
	}
}

func testStep(
	opts terraform.ContextOpts,
	state *terraform.State,
	step TestStep) (*terraform.State, error) {
	// Write the configuration
	cfgF, err := ioutil.TempFile("", "tf-test")
	if err != nil {
		return state, fmt.Errorf(
			"Error creating temporary file for config: %s", err)
	}
	cfgPath := cfgF.Name() + ".tf"
	cfgF.Close()
	os.Remove(cfgF.Name())

	cfgF, err = os.Create(cfgPath)
	if err != nil {
		return state, fmt.Errorf(
			"Error creating temporary file for config: %s", err)
	}
	defer os.Remove(cfgPath)

	_, err = io.Copy(cfgF, strings.NewReader(step.Config))
	cfgF.Close()
	if err != nil {
		return state, fmt.Errorf(
			"Error creating temporary file for config: %s", err)
	}

	// Parse the configuration
	config, err := config.Load(cfgPath)
	if err != nil {
		return state, fmt.Errorf(
			"Error parsing configuration: %s", err)
	}

	// Build the context
	opts.Config = config
	ctx := terraform.NewContext(&opts)
	if ws, es := ctx.Validate(); len(ws) > 0 || len(es) > 0 {
		return state, fmt.Errorf(
			"Configuration is invalid.\n\nWarnings: %#v\n\nErrors: %#v",
			ws, es)
	}

	// Plan!
	if _, err := ctx.Plan(&terraform.PlanOpts{Destroy: step.Destroy}); err != nil {
		return state, fmt.Errorf(
			"Error planning: %s", err)
	}

	// Apply!
	state, err = ctx.Apply()
	if err != nil {
		return state, fmt.Errorf("Error applying: %s", err)
	}

	// Check! Excitement!
	if step.Check != nil {
		if err = step.Check(state); err != nil {
			err = fmt.Errorf("Check failed: %s", err)
		}
	}

	return state, err
}

// TestT is the interface used to handle the test lifecycle of a test.
//
// Users should just use a *testing.T object, which implements this.
type TestT interface {
	Error(args ...interface{})
	Fatal(args ...interface{})
	Skip(args ...interface{})
}

// This is set to true by unit tests to alter some behavior
var testTesting = false