// 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 deploy

import (
	"github.com/blang/semver"
	"github.com/pkg/errors"
	uuid "github.com/satori/go.uuid"

	"github.com/pulumi/pulumi/pkg/diag"
	"github.com/pulumi/pulumi/pkg/resource"
	"github.com/pulumi/pulumi/pkg/resource/deploy/providers"
	"github.com/pulumi/pulumi/pkg/resource/graph"
	"github.com/pulumi/pulumi/pkg/resource/plugin"
	"github.com/pulumi/pulumi/pkg/tokens"
	"github.com/pulumi/pulumi/pkg/util/contract"
)

// Options controls the planning and deployment process.
type Options struct {
	Events   Events // an optional events callback interface.
	Parallel int    // the degree of parallelism for resource operations (<=1 for serial).
}

// DegreeOfParallelism returns the degree of parallelism that should be used during the
// planning and deployment process.
func (o Options) DegreeOfParallelism() int {
	if o.Parallel <= 1 {
		return 1
	}
	return o.Parallel
}

// Events is an interface that can be used to hook interesting engine/planning events.
type Events interface {
	OnResourceStepPre(step Step) (interface{}, error)
	OnResourceStepPost(ctx interface{}, step Step, status resource.Status, err error) error
	OnResourceOutputs(step Step) error
}

// PlanSummary is an interface for summarizing the progress of a plan.
type PlanSummary interface {
	Steps() int
	Creates() map[resource.URN]bool
	Updates() map[resource.URN]bool
	Replaces() map[resource.URN]bool
	Deletes() map[resource.URN]bool
	Sames() map[resource.URN]bool
}

// PlanPendingOperationsError is an error returned from `NewPlan` if there exist pending operations in the
// snapshot that we are preparing to operate upon. The engine does not allow any operations to be pending
// when operating on a snapshot.
type PlanPendingOperationsError struct {
	Operations []resource.Operation
}

func (p PlanPendingOperationsError) Error() string {
	return "one or more operations are currently pending"
}

// Plan is the output of analyzing resource graphs and contains the steps necessary to perform an infrastructure
// deployment.  A plan can be generated out of whole cloth from a resource graph -- in the case of new deployments --
// however, it can alternatively be generated by diffing two resource graphs -- in the case of updates to existing
// stacks (presumably more common).  The plan contains step objects that can be used to drive a deployment.
type Plan struct {
	ctx       *plugin.Context                  // the plugin context (for provider operations).
	target    *Target                          // the deployment target.
	prev      *Snapshot                        // the old resource snapshot for comparison.
	olds      map[resource.URN]*resource.State // a map of all old resources.
	source    Source                           // the source of new resources.
	analyzers []tokens.QName                   // the analyzers to run during this plan's generation.
	preview   bool                             // true if this plan is to be previewed rather than applied.
	depGraph  *graph.DependencyGraph           // the dependency graph of the old snapshot
	providers *providers.Registry              // the provider registry for this plan.
}

// addDefaultProviders adds any necessary default provider definitions and references to the given snapshot. Version
// information for these providers is sourced from the snapshot's manifest; inputs parameters are sourced from the
// stack's configuration.
func addDefaultProviders(target *Target, source Source, prev *Snapshot) error {
	if prev == nil {
		return nil
	}

	// Pull the versions we'll use for default providers from the snapshot's manifest.
	defaultProviderVersions := make(map[tokens.Package]*semver.Version)
	for _, p := range prev.Manifest.Plugins {
		defaultProviderVersions[tokens.Package(p.Name)] = p.Version
	}

	// Determine the necessary set of default providers and inject references to default providers as appropriate.
	//
	// We do this by scraping the snapshot for custom resources that does not reference a provider and adding
	// default providers for these resources' packages. Each of these resources is rewritten to reference the default
	// provider for its package.
	//
	// The configuration for each default provider is pulled from the stack's configuration information.
	var defaultProviders []*resource.State
	defaultProviderRefs := make(map[tokens.Package]providers.Reference)
	for _, res := range prev.Resources {
		if providers.IsProviderType(res.URN.Type()) || !res.Custom || res.Provider != "" {
			continue
		}

		pkg := res.URN.Type().Package()
		ref, ok := defaultProviderRefs[pkg]
		if !ok {
			cfg, err := target.GetPackageConfig(pkg)
			if err != nil {
				return errors.Errorf("could not fetch configuration for default provider '%v'", pkg)
			}

			inputs := make(resource.PropertyMap)
			for k, v := range cfg {
				inputs[resource.PropertyKey(k.Name())] = resource.NewStringProperty(v)
			}
			if version, ok := defaultProviderVersions[pkg]; ok {
				inputs["version"] = resource.NewStringProperty(version.String())
			}

			urn, id := defaultProviderURN(target, source, pkg), resource.ID(uuid.NewV4().String())
			ref, err = providers.NewReference(urn, id)
			contract.Assert(err == nil)

			provider := &resource.State{
				Type:   urn.Type(),
				URN:    urn,
				Custom: true,
				ID:     id,
				Inputs: inputs,
			}
			defaultProviders = append(defaultProviders, provider)
			defaultProviderRefs[pkg] = ref
		}
		res.Provider = ref.String()
	}

	// If any default providers are necessary, prepend their definitions to the snapshot's resources. This trivially
	// guarantees that all default provider references name providers that precede the referent in the snapshot.
	if len(defaultProviders) != 0 {
		prev.Resources = append(defaultProviders, prev.Resources...)
	}

	return nil
}

// NewPlan creates a new deployment plan from a resource snapshot plus a package to evaluate.
//
// From the old and new states, it understands how to orchestrate an evaluation and analyze the resulting resources.
// The plan may be used to simply inspect a series of operations, or actually perform them; these operations are
// generated based on analysis of the old and new states.  If a resource exists in new, but not old, for example, it
// results in a create; if it exists in both, but is different, it results in an update; and so on and so forth.
//
// Note that a plan uses internal concurrency and parallelism in various ways, so it must be closed if for some reason
// a plan isn't carried out to its final conclusion.  This will result in cancelation and reclamation of OS resources.
func NewPlan(ctx *plugin.Context, target *Target, prev *Snapshot, source Source, analyzers []tokens.QName,
	preview bool) (*Plan, error) {

	contract.Assert(ctx != nil)
	contract.Assert(target != nil)
	contract.Assert(source != nil)

	// Add any necessary default provider references to the previous snapshot in order to accommodate stacks that were
	// created prior to the changes that added first-class providers. We do this here rather than in the migration
	// package s.t. the inputs to any default providers (which we fetch from the stacks's configuration) are as
	// accurate as possible.
	if err := addDefaultProviders(target, source, prev); err != nil {
		return nil, err
	}

	var depGraph *graph.DependencyGraph
	var oldResources []*resource.State

	// Produce a map of all old resources for fast resources.
	olds := make(map[resource.URN]*resource.State)
	if prev != nil {
		if prev.PendingOperations != nil {
			return nil, PlanPendingOperationsError{prev.PendingOperations}
		}
		oldResources = prev.Resources

		for _, oldres := range oldResources {
			// Ignore resources that are pending deletion; these should not be recorded in the LUT.
			if oldres.Delete {
				continue
			}

			urn := oldres.URN
			contract.Assert(olds[urn] == nil)
			olds[urn] = oldres
		}

		depGraph = graph.NewDependencyGraph(oldResources)
	}

	// Create a new provider registry. Although we really only need to pass in any providers that were present in the
	// old resource list, the registry itself will filter out other sorts of resources when processing the prior state,
	// so we just pass all of the old resources.
	reg, err := providers.NewRegistry(ctx.Host, oldResources, preview)
	if err != nil {
		return nil, err
	}

	return &Plan{
		ctx:       ctx,
		target:    target,
		prev:      prev,
		olds:      olds,
		source:    source,
		analyzers: analyzers,
		preview:   preview,
		depGraph:  depGraph,
		providers: reg,
	}, nil
}

func (p *Plan) Ctx() *plugin.Context                   { return p.ctx }
func (p *Plan) Target() *Target                        { return p.target }
func (p *Plan) Diag() diag.Sink                        { return p.ctx.Diag }
func (p *Plan) Prev() *Snapshot                        { return p.prev }
func (p *Plan) Olds() map[resource.URN]*resource.State { return p.olds }
func (p *Plan) Source() Source                         { return p.source }
func (p *Plan) IsRefresh() bool                        { return p.source.IsRefresh() }

func (p *Plan) SignalCancellation() error {
	return p.ctx.Host.SignalCancellation()
}

func (p *Plan) GetProvider(ref providers.Reference) (plugin.Provider, bool) {
	return p.providers.GetProvider(ref)
}

// generateURN generates a resource's URN from its parent, type, and name under the scope of the plan's stack and
// project.
func (p *Plan) generateURN(parent resource.URN, ty tokens.Type, name tokens.QName) resource.URN {
	// Use the resource goal state name to produce a globally unique URN.
	parentType := tokens.Type("")
	if parent != "" && parent.Type() != resource.RootStackType {
		// Skip empty parents and don't use the root stack type; otherwise, use the full qualified type.
		parentType = parent.QualifiedType()
	}

	return resource.NewURN(p.Target().Name, p.source.Project(), parentType, ty, name)
}

// defaultProviderURN generates the URN for the global provider given a package.
func defaultProviderURN(target *Target, source Source, pkg tokens.Package) resource.URN {
	return resource.NewURN(target.Name, source.Project(), "", providers.MakeProviderType(pkg), "default")
}