package terraform

import (
	"fmt"
	"log"
	"strings"

	"github.com/hashicorp/go-multierror"
	"github.com/hashicorp/terraform/config/module"
	"github.com/hashicorp/terraform/dag"
)

// TODO: return the transformers and append them to the list, so we don't lose the log steps
func TransformProviders(providers []string, concrete ConcreteProviderNodeFunc, mod *module.Tree) GraphTransformer {
	return GraphTransformMulti(
		// Add providers from the config
		&ProviderConfigTransformer{
			Module:    mod,
			Providers: providers,
			Concrete:  concrete,
		},
		// Attach configuration to each provider instance
		&AttachProviderConfigTransformer{
			Module: mod,
		},
		// Add any remaining missing providers
		&MissingProviderTransformer{
			Providers: providers,
			Concrete:  concrete,
		},
		// Connect the providers
		&ProviderTransformer{},
		// Disable unused providers
		&DisableProviderTransformer{},
		// Connect provider to their parent provider nodes
		&ParentProviderTransformer{},
	)
}

// GraphNodeProvider is an interface that nodes that can be a provider
// must implement.
// ProviderName returns the name of the provider this satisfies.
// Name returns the full name of the provider in the config.
type GraphNodeProvider interface {
	ProviderName() string
	Name() string
}

// GraphNodeCloseProvider is an interface that nodes that can be a close
// provider must implement. The CloseProviderName returned is the name of
// the provider they satisfy.
type GraphNodeCloseProvider interface {
	CloseProviderName() string
}

// GraphNodeProviderConsumer is an interface that nodes that require
// a provider must implement. ProvidedBy must return the name of the provider
// to use.
type GraphNodeProviderConsumer interface {
	// TODO: make this return s string instead of a []string
	ProvidedBy() []string
	// Set the resolved provider address for this resource.
	SetProvider(string)
}

// ProviderTransformer is a GraphTransformer that maps resources to
// providers within the graph. This will error if there are any resources
// that don't map to proper resources.
type ProviderTransformer struct{}

func (t *ProviderTransformer) Transform(g *Graph) error {
	// Go through the other nodes and match them to providers they need
	var err error
	m := providerVertexMap(g)
	for _, v := range g.Vertices() {
		if pv, ok := v.(GraphNodeProviderConsumer); ok {
			p := pv.ProvidedBy()[0]

			key := providerMapKey(p, pv)
			target := m[key]

			sp, ok := pv.(GraphNodeSubPath)
			if !ok && target == nil {
				// no target, and no path to walk up
				err = multierror.Append(err, fmt.Errorf(
					"%s: provider %s couldn't be found",
					dag.VertexName(v), p))
				break
			}

			// if we don't have a provider at this level, walk up the path looking for one
			for i := 1; target == nil; i++ {
				path := normalizeModulePath(sp.Path())
				if len(path) < i {
					break
				}

				key = ResolveProviderName(p, path[:len(path)-i])
				target = m[key]
				if target != nil {
					break
				}
			}

			if target == nil {
				err = multierror.Append(err, fmt.Errorf(
					"%s: provider %s couldn't be found",
					dag.VertexName(v), p))
				break
			}

			log.Printf("[DEBUG] resource %s using provider %s", dag.VertexName(pv), key)
			pv.SetProvider(key)
			g.Connect(dag.BasicEdge(v, target))
		}
	}

	return err
}

// CloseProviderTransformer is a GraphTransformer that adds nodes to the
// graph that will close open provider connections that aren't needed anymore.
// A provider connection is not needed anymore once all depended resources
// in the graph are evaluated.
type CloseProviderTransformer struct{}

// FIXME: this doesn't close providers if the root provider is disabled
func (t *CloseProviderTransformer) Transform(g *Graph) error {
	pm := providerVertexMap(g)
	cpm := make(map[string]*graphNodeCloseProvider)
	var err error

	for _, v := range pm {
		p := v.(GraphNodeProvider)

		// get the close provider of this type if we alread created it
		closer := cpm[p.ProviderName()]

		if closer == nil {
			// create a closer for this provider type
			closer = &graphNodeCloseProvider{ProviderNameValue: p.ProviderName()}
			g.Add(closer)
			cpm[p.ProviderName()] = closer
		}

		// Close node depends on the provider itself
		// this is added unconditionally, so it will connect to all instances
		// of the provider. Extra edges will be removed by transitive
		// reduction.
		g.Connect(dag.BasicEdge(closer, p))

		// connect all the provider's resources to the close node
		for _, s := range g.UpEdges(p).List() {
			if _, ok := s.(GraphNodeProviderConsumer); ok {
				g.Connect(dag.BasicEdge(closer, s))
			}
		}
	}

	return err
}

// MissingProviderTransformer is a GraphTransformer that adds nodes for all
// required providers into the graph. Specifically, it creates provider
// configuration nodes for all the providers that we support. These are pruned
// later during an optimization pass.
type MissingProviderTransformer struct {
	// Providers is the list of providers we support.
	Providers []string

	// Concrete, if set, overrides how the providers are made.
	Concrete ConcreteProviderNodeFunc
}

func (t *MissingProviderTransformer) Transform(g *Graph) error {
	// Initialize factory
	if t.Concrete == nil {
		t.Concrete = func(a *NodeAbstractProvider) dag.Vertex {
			return a
		}
	}

	var err error
	m := providerVertexMap(g)
	for _, v := range g.Vertices() {
		pv, ok := v.(GraphNodeProviderConsumer)
		if !ok {
			continue
		}

		p := pv.ProvidedBy()[0]
		key := ResolveProviderName(p, nil)
		provider := m[key]

		// we already have it
		if provider != nil {
			continue
		}

		// we don't implicitly create aliased providers
		if strings.Contains(p, ".") {
			log.Println("[DEBUG] not adding missing provider alias", p)
			continue
		}

		// create the misisng top-level provider
		provider = t.Concrete(&NodeAbstractProvider{
			NameValue: p,
		}).(dag.Vertex)

		m[key] = g.Add(provider)
	}

	return err
}

// ParentProviderTransformer connects provider nodes to their parents.
//
// This works by finding nodes that are both GraphNodeProviders and
// GraphNodeSubPath. It then connects the providers to their parent
// path. The parent provider is always at the root level.
type ParentProviderTransformer struct{}

func (t *ParentProviderTransformer) Transform(g *Graph) error {
	pm := providerVertexMap(g)
	for _, v := range g.Vertices() {
		// Only care about providers
		pn, ok := v.(GraphNodeProvider)
		if !ok || pn.ProviderName() == "" {
			continue
		}

		// Also require a subpath, if there is no subpath then we
		// can't have a parent.
		if pn, ok := v.(GraphNodeSubPath); ok {
			if len(normalizeModulePath(pn.Path())) <= 1 {
				continue
			}
		}

		// this provider may be disabled, but we can only get it's name from
		// the ProviderName string
		name := ResolveProviderName(strings.SplitN(pn.ProviderName(), " ", 2)[0], nil)
		parent := pm[name]
		if parent != nil {
			g.Connect(dag.BasicEdge(v, parent))
		}

	}
	return nil
}

// PruneProviderTransformer is a GraphTransformer that prunes all the
// providers that aren't needed from the graph. A provider is unneeded if
// no resource or module is using that provider.
type PruneProviderTransformer struct{}

func (t *PruneProviderTransformer) Transform(g *Graph) error {
	for _, v := range g.Vertices() {
		// We only care about the providers
		if pn, ok := v.(GraphNodeProvider); !ok || pn.ProviderName() == "" {
			continue
		}
		// Does anything depend on this? If not, then prune it.
		if s := g.UpEdges(v); s.Len() == 0 {
			if nv, ok := v.(dag.NamedVertex); ok {
				log.Printf("[DEBUG] Pruning provider with no dependencies: %s", nv.Name())
			}
			g.Remove(v)
		}
	}

	return nil
}

// providerMapKey is a helper that gives us the key to use for the
// maps returned by things such as providerVertexMap.
func providerMapKey(k string, v dag.Vertex) string {
	// we create a dummy provider to
	var path []string
	if sp, ok := v.(GraphNodeSubPath); ok {
		path = normalizeModulePath(sp.Path())
	}
	return ResolveProviderName(k, path)
}

func providerVertexMap(g *Graph) map[string]dag.Vertex {
	m := make(map[string]dag.Vertex)
	for _, v := range g.Vertices() {
		if pv, ok := v.(GraphNodeProvider); ok {
			// TODO:  The Name may have meta info, like " (disabled)"
			name := strings.SplitN(pv.Name(), " ", 2)[0]
			m[name] = v
		}
	}

	return m
}

func closeProviderVertexMap(g *Graph) map[string]dag.Vertex {
	m := make(map[string]dag.Vertex)
	for _, v := range g.Vertices() {
		if pv, ok := v.(GraphNodeCloseProvider); ok {
			m[pv.CloseProviderName()] = v
		}
	}

	return m
}

type graphNodeCloseProvider struct {
	ProviderNameValue string
}

func (n *graphNodeCloseProvider) Name() string {
	return fmt.Sprintf("provider.%s (close)", n.ProviderNameValue)
}

// GraphNodeEvalable impl.
func (n *graphNodeCloseProvider) EvalTree() EvalNode {
	return CloseProviderEvalTree(n.ProviderNameValue)
}

// GraphNodeDependable impl.
func (n *graphNodeCloseProvider) DependableName() []string {
	return []string{n.Name()}
}

func (n *graphNodeCloseProvider) CloseProviderName() string {
	return n.ProviderNameValue
}

// GraphNodeDotter impl.
func (n *graphNodeCloseProvider) DotNode(name string, opts *dag.DotOpts) *dag.DotNode {
	if !opts.Verbose {
		return nil
	}
	return &dag.DotNode{
		Name: name,
		Attrs: map[string]string{
			"label": n.Name(),
			"shape": "diamond",
		},
	}
}

// RemovableIfNotTargeted
func (n *graphNodeCloseProvider) RemoveIfNotTargeted() bool {
	// We need to add this so that this node will be removed if
	// it isn't targeted or a dependency of a target.
	return true
}

// graphNodeProviderConsumerDummy is a struct that never enters the real
// graph (though it could to no ill effect). It implements
// GraphNodeProviderConsumer and GraphNodeSubpath as a way to force
// certain transformations.
type graphNodeProviderConsumerDummy struct {
	ProviderValue string
	PathValue     []string
}

func (n *graphNodeProviderConsumerDummy) Path() []string {
	return n.PathValue
}

func (n *graphNodeProviderConsumerDummy) ProvidedBy() []string {
	return []string{n.ProviderValue}
}

func (n *graphNodeProviderConsumerDummy) SetProvider(string) {}