// Copyright 2016-2018, Pulumi Corporation.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package engine

import (
	"bytes"
	"context"
	"fmt"
	"os"
	"sync"

	"github.com/golang/glog"
	"github.com/opentracing/opentracing-go"
	"github.com/pkg/errors"
	"github.com/pulumi/pulumi/pkg/diag"
	"github.com/pulumi/pulumi/pkg/diag/colors"
	"github.com/pulumi/pulumi/pkg/resource"
	"github.com/pulumi/pulumi/pkg/resource/deploy"
	"github.com/pulumi/pulumi/pkg/resource/plugin"
	"github.com/pulumi/pulumi/pkg/tokens"
	"github.com/pulumi/pulumi/pkg/util/contract"
	"github.com/pulumi/pulumi/pkg/workspace"
)

// ProjectInfoContext returns information about the current project, including its pwd, main, and plugin context.
func ProjectInfoContext(projinfo *Projinfo, host plugin.Host, config plugin.ConfigSource, pluginEvents plugin.Events,
	diag diag.Sink, tracingSpan opentracing.Span) (string, string, *plugin.Context, error) {
	contract.Require(projinfo != nil, "projinfo")

	// If the package contains an override for the main entrypoint, use it.
	pwd, main, err := projinfo.GetPwdMain()
	if err != nil {
		return "", "", nil, err
	}

	// Create a context for plugins.
	ctx, err := plugin.NewContext(diag, host, config, pluginEvents, pwd, projinfo.Proj.RuntimeInfo.Options(),
		tracingSpan)
	if err != nil {
		return "", "", nil, err
	}

	return pwd, main, ctx, nil
}

// newPlanContext creates a context for a subsequent planning operation.  Callers must call Close on the
// resulting context object once they have completed the associated planning operation.
func newPlanContext(u UpdateInfo, opName string, parentSpan opentracing.SpanContext) (*planContext, error) {
	contract.Require(u != nil, "u")

	// Create a root span for the operation
	opts := []opentracing.StartSpanOption{}
	if opName != "" {
		opts = append(opts, opentracing.Tag{Key: "operation", Value: opName})
	}
	if parentSpan != nil {
		opts = append(opts, opentracing.ChildOf(parentSpan))
	}
	tracingSpan := opentracing.StartSpan("pulumi-plan", opts...)

	return &planContext{
		Update:      u,
		TracingSpan: tracingSpan,
	}, nil
}

type planContext struct {
	Update      UpdateInfo       // The update being processed.
	TracingSpan opentracing.Span // An OpenTracing span to parent plan operations within.
}

func (ctx *planContext) Close() {
	ctx.TracingSpan.Finish()
}

// planOptions includes a full suite of options for performing a plan and/or deploy operation.
type planOptions struct {
	UpdateOptions

	// SourceFunc is a factory that returns an EvalSource to use during planning.  This is the thing that
	// creates resources to compare against the current checkpoint state (e.g., by evaluating a program, etc).
	SourceFunc planSourceFunc

	SkipOutputs bool         // true if we we should skip printing outputs separately.
	DOT         bool         // true if we should print the DOT file for this plan.
	Events      eventEmitter // the channel to write events from the engine to.
	Diag        diag.Sink    // the sink to use for diag'ing.
}

// planSourceFunc is a callback that will be used to prepare for, and evaluate, the "new" state for a stack.
type planSourceFunc func(
	opts planOptions, proj *workspace.Project, pwd, main string,
	target *deploy.Target, plugctx *plugin.Context, dryRun bool) (deploy.Source, error)

// plan just uses the standard logic to parse arguments, options, and to create a snapshot and plan.
func plan(ctx *Context, info *planContext, opts planOptions, dryRun bool) (*planResult, error) {
	contract.Assert(info != nil)
	contract.Assert(info.Update != nil)
	contract.Assert(opts.SourceFunc != nil)

	// If this isn't a dry run, we will need to record plugin events, so that we persist them in the checkpoint. If
	// we're just doing a dry run, we don't actually need to persist anything (and indeed trying to do so would fail).
	var pluginEvents plugin.Events
	if !dryRun {
		pluginEvents = &pluginActions{ctx}
	}

	// First, load the package metadata and the deployment target in preparation for executing the package's program
	// and creating resources.  This includes fetching its pwd and main overrides.
	proj, target := info.Update.GetProject(), info.Update.GetTarget()
	contract.Assert(proj != nil)
	contract.Assert(target != nil)
	projinfo := &Projinfo{Proj: proj, Root: info.Update.GetRoot()}
	pwd, main, plugctx, err := ProjectInfoContext(projinfo, opts.host, target, pluginEvents, opts.Diag, info.TracingSpan)
	if err != nil {
		return nil, err
	}

	// Now create the state source.  This may issue an error if it can't create the source.  This entails,
	// for example, loading any plugins which will be required to execute a program, among other things.
	source, err := opts.SourceFunc(opts, proj, pwd, main, target, plugctx, dryRun)
	if err != nil {
		return nil, err
	}

	// If there are any analyzers in the project file, add them.
	var analyzers []tokens.QName
	if as := projinfo.Proj.Analyzers; as != nil {
		for _, a := range *as {
			analyzers = append(analyzers, a)
		}
	}

	// Append any analyzers from the command line.
	for _, a := range opts.Analyzers {
		analyzers = append(analyzers, tokens.QName(a))
	}

	// Generate a plan; this API handles all interesting cases (create, update, delete).
	plan, err := deploy.NewPlan(plugctx, target, target.Snapshot, source, analyzers, dryRun)
	if err != nil {
		return nil, err
	}
	return &planResult{
		Ctx:     info,
		Plugctx: plugctx,
		Plan:    plan,
		Options: opts,
	}, nil
}

type planResult struct {
	Ctx     *planContext    // plan context information.
	Plugctx *plugin.Context // the context containing plugins and their state.
	Plan    *deploy.Plan    // the plan created by this command.
	Options planOptions     // the options used during planning.
}

// Chdir changes the directory so that all operations from now on are relative to the project we are working with.
// It returns a function that, when run, restores the old working directory.
func (res *planResult) Chdir() (func(), error) {
	pwd := res.Plugctx.Pwd
	if pwd == "" {
		return func() {}, nil
	}
	oldpwd, err := os.Getwd()
	if err != nil {
		return nil, err
	}
	if err = os.Chdir(pwd); err != nil {
		return nil, errors.Wrapf(err, "could not change to the project working directory")
	}
	return func() {
		// Restore the working directory after planning completes.
		cderr := os.Chdir(oldpwd)
		contract.IgnoreError(cderr)
	}, nil
}

// Walk enumerates all steps in the plan, calling out to the provided action at each step.  It returns four things: the
// resulting Snapshot, no matter whether an error occurs or not; an error, if something went wrong; the step that
// failed, if the error is non-nil; and finally the state of the resource modified in the failing step.
func (res *planResult) Walk(cancelCtx *Context, events deploy.Events, preview bool) (deploy.PlanSummary, error) {
	opts := deploy.Options{
		Events:   events,
		Parallel: res.Options.Parallel,
	}

	src, err := res.Plan.Source().Iterate(opts, res.Plan)
	if err != nil {
		return nil, err
	}

	ctx, cancelFunc := context.WithCancel(context.Background())
	done := make(chan bool)
	var summary deploy.PlanSummary
	go func() {
		planExec := deploy.NewPlanExecutor(ctx, res.Plan, opts, preview, src)
		err = planExec.Execute()
		summary = planExec.Summary()
		close(done)
	}()

	// Asynchronously listen for cancellation, and deliver that signal to plan.
	go func() {
		select {
		case <-cancelCtx.Cancel.Canceled():
			// Cancel the plan executor's context, so it begins to shut down.
			cancelFunc()
			cancelErr := res.Plan.SignalCancellation()
			if cancelErr != nil {
				glog.V(3).Infof("Attempted to signal cancellation to resource providers, but failed: %s",
					cancelErr.Error())
			}
		case <-done:
			return
		}
	}()

	select {
	case <-cancelCtx.Cancel.Terminated():
		return summary, cancelCtx.Cancel.TerminateErr()

	case <-done:
		return summary, err
	}
}

func (res *planResult) Close() error {
	return res.Plugctx.Close()
}

// printPlan prints the plan's result to the plan's Options.Events stream.
func printPlan(ctx *Context, result *planResult, dryRun bool) (ResourceChanges, error) {
	result.Options.Events.preludeEvent(dryRun, result.Ctx.Update.GetTarget().Config)

	// Walk the plan's steps and and pretty-print them out.
	actions := newPlanActions(result.Options)
	_, err := result.Walk(ctx, actions, true)
	if err != nil {
		return nil, errors.New("an error occurred while advancing the preview")
	}

	// Emit an event with a summary of operation counts.
	changes := ResourceChanges(actions.Ops)
	result.Options.Events.previewSummaryEvent(changes)
	return changes, nil
}

type planActions struct {
	Refresh bool
	Ops     map[deploy.StepOp]int
	Opts    planOptions
	Seen    map[resource.URN]deploy.Step
	MapLock sync.Mutex
}

func newPlanActions(opts planOptions) *planActions {
	return &planActions{
		Ops:  make(map[deploy.StepOp]int),
		Opts: opts,
		Seen: make(map[resource.URN]deploy.Step),
	}
}

func (acts *planActions) OnResourceStepPre(step deploy.Step) (interface{}, error) {
	acts.MapLock.Lock()
	acts.Seen[step.URN()] = step
	acts.MapLock.Unlock()
	acts.Opts.Events.resourcePreEvent(step, true /*planning*/, acts.Opts.Debug)

	// Warn the user if they're not updating a resource whose initialization failed.
	if step.Op() == deploy.OpSame && len(step.Old().InitErrors) > 0 {
		indent := "         "

		// TODO: Move indentation to the display logic, instead of doing it ourselves.
		var warning bytes.Buffer
		warning.WriteString("This resource failed to initialize in a previous deployment. It is recommended\n")
		warning.WriteString(indent + "to update it to fix these issues:\n")
		for i, err := range step.Old().InitErrors {
			warning.WriteString(colors.SpecImportant + indent + fmt.Sprintf("  - Problem #%d", i+1) +
				colors.Reset + " " + err + "\n")
		}
		acts.Opts.Diag.Warningf(diag.RawMessage(step.URN(), warning.String()))
	}

	return nil, nil
}

func (acts *planActions) OnResourceStepPost(ctx interface{},
	step deploy.Step, status resource.Status, err error) error {
	acts.MapLock.Lock()
	assertSeen(acts.Seen, step)
	acts.MapLock.Unlock()

	if err != nil {
		acts.Opts.Diag.Errorf(diag.GetPreviewFailedError(step.URN()), err)
	} else {
		// Track the operation if shown and/or if it is a logically meaningful operation.
		if step.Logical() {
			acts.MapLock.Lock()
			acts.Ops[step.Op()]++
			acts.MapLock.Unlock()
		}

		_ = acts.OnResourceOutputs(step)
	}

	return nil
}

func (acts *planActions) OnResourceOutputs(step deploy.Step) error {
	acts.MapLock.Lock()
	assertSeen(acts.Seen, step)
	acts.MapLock.Unlock()
	// Print the resource outputs separately, unless this is a refresh in which case they are already printed.
	if !acts.Opts.SkipOutputs {
		acts.Opts.Events.resourceOutputsEvent(step, true /*planning*/, acts.Opts.Debug)
	}

	return nil
}

func assertSeen(seen map[resource.URN]deploy.Step, step deploy.Step) {
	_, has := seen[step.URN()]
	contract.Assertf(has, "URN '%v' had not been marked as seen", step.URN())
}