package terraform

import (
	"fmt"

	"github.com/zclconf/go-cty/cty"

	"github.com/hashicorp/terraform/addrs"
	"github.com/hashicorp/terraform/configs"
	"github.com/hashicorp/terraform/plans"
	"github.com/hashicorp/terraform/providers"
	"github.com/hashicorp/terraform/states"
	"github.com/hashicorp/terraform/tfdiags"
)

// NodeApplyableResourceInstance represents a resource instance that is
// "applyable": it is ready to be applied and is represented by a diff.
//
// This node is for a specific instance of a resource. It will usually be
// accompanied in the graph by a NodeApplyableResource representing its
// containing resource, and should depend on that node to ensure that the
// state is properly prepared to receive changes to instances.
type NodeApplyableResourceInstance struct {
	*NodeAbstractResourceInstance

	destroyNode      GraphNodeDestroyerCBD
	graphNodeDeposer // implementation of GraphNodeDeposer
}

var (
	_ GraphNodeResource           = (*NodeApplyableResourceInstance)(nil)
	_ GraphNodeResourceInstance   = (*NodeApplyableResourceInstance)(nil)
	_ GraphNodeCreator            = (*NodeApplyableResourceInstance)(nil)
	_ GraphNodeReferencer         = (*NodeApplyableResourceInstance)(nil)
	_ GraphNodeDeposer            = (*NodeApplyableResourceInstance)(nil)
	_ GraphNodeEvalable           = (*NodeApplyableResourceInstance)(nil)
	_ GraphNodeAttachDependencies = (*NodeApplyableResourceInstance)(nil)
)

// GraphNodeAttachDestroyer
func (n *NodeApplyableResourceInstance) AttachDestroyNode(d GraphNodeDestroyerCBD) {
	n.destroyNode = d
}

// createBeforeDestroy checks this nodes config status and the status af any
// companion destroy node for CreateBeforeDestroy.
func (n *NodeApplyableResourceInstance) createBeforeDestroy() bool {
	cbd := false

	if n.Config != nil && n.Config.Managed != nil {
		cbd = n.Config.Managed.CreateBeforeDestroy
	}

	if n.destroyNode != nil {
		cbd = cbd || n.destroyNode.CreateBeforeDestroy()
	}

	return cbd
}

// GraphNodeCreator
func (n *NodeApplyableResourceInstance) CreateAddr() *addrs.AbsResourceInstance {
	addr := n.ResourceInstanceAddr()
	return &addr
}

// GraphNodeReferencer, overriding NodeAbstractResourceInstance
func (n *NodeApplyableResourceInstance) References() []*addrs.Reference {
	// Start with the usual resource instance implementation
	ret := n.NodeAbstractResourceInstance.References()

	// Applying a resource must also depend on the destruction of any of its
	// dependencies, since this may for example affect the outcome of
	// evaluating an entire list of resources with "count" set (by reducing
	// the count).
	//
	// However, we can't do this in create_before_destroy mode because that
	// would create a dependency cycle. We make a compromise here of requiring
	// changes to be updated across two applies in this case, since the first
	// plan will use the old values.
	if !n.createBeforeDestroy() {
		for _, ref := range ret {
			switch tr := ref.Subject.(type) {
			case addrs.ResourceInstance:
				newRef := *ref // shallow copy so we can mutate
				newRef.Subject = tr.Phase(addrs.ResourceInstancePhaseDestroy)
				newRef.Remaining = nil // can't access attributes of something being destroyed
				ret = append(ret, &newRef)
			case addrs.Resource:
				newRef := *ref // shallow copy so we can mutate
				newRef.Subject = tr.Phase(addrs.ResourceInstancePhaseDestroy)
				newRef.Remaining = nil // can't access attributes of something being destroyed
				ret = append(ret, &newRef)
			}
		}
	}

	return ret
}

// GraphNodeAttachDependencies
func (n *NodeApplyableResourceInstance) AttachDependencies(deps []addrs.AbsResource) {
	n.Dependencies = deps
}

// GraphNodeEvalable
func (n *NodeApplyableResourceInstance) EvalTree() EvalNode {
	addr := n.ResourceInstanceAddr()

	if n.Config == nil {
		// This should not be possible, but we've got here in at least one
		// case as discussed in the following issue:
		//    https://github.com/hashicorp/terraform/issues/21258
		// To avoid an outright crash here, we'll instead return an explicit
		// error.
		var diags tfdiags.Diagnostics
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"Resource node has no configuration attached",
			fmt.Sprintf(
				"The graph node for %s has no configuration attached to it. This suggests a bug in Terraform's apply graph builder; please report it!",
				addr,
			),
		))
		err := diags.Err()
		return &EvalReturnError{
			Error: &err,
		}
	}

	// Eval info is different depending on what kind of resource this is
	switch n.Config.Mode {
	case addrs.ManagedResourceMode:
		return n.evalTreeManagedResource(addr)
	case addrs.DataResourceMode:
		return n.evalTreeDataResource(addr)
	default:
		panic(fmt.Errorf("unsupported resource mode %s", n.Config.Mode))
	}
}

func (n *NodeApplyableResourceInstance) evalTreeDataResource(addr addrs.AbsResourceInstance) EvalNode {
	var provider providers.Interface
	var providerSchema *ProviderSchema
	var change *plans.ResourceInstanceChange
	var state *states.ResourceInstanceObject

	return &EvalSequence{
		Nodes: []EvalNode{
			&EvalGetProvider{
				Addr:   n.ResolvedProvider,
				Output: &provider,
				Schema: &providerSchema,
			},

			// Get the saved diff for apply
			&EvalReadDiff{
				Addr:           addr.Resource,
				ProviderSchema: &providerSchema,
				Change:         &change,
			},

			// Stop early if we don't actually have a diff
			&EvalIf{
				If: func(ctx EvalContext) (bool, error) {
					if change == nil {
						return true, EvalEarlyExitError{}
					}
					return true, nil
				},
				Then: EvalNoop{},
			},

			// In this particular call to EvalReadData we include our planned
			// change, which signals that we expect this read to complete fully
			// with no unknown values; it'll produce an error if not.
			&EvalReadData{
				Addr:           addr.Resource,
				Config:         n.Config,
				Planned:        &change, // setting this indicates that the result must be complete
				Provider:       &provider,
				ProviderAddr:   n.ResolvedProvider,
				ProviderSchema: &providerSchema,
				OutputState:    &state,
			},

			&EvalWriteState{
				Addr:           addr.Resource,
				ProviderAddr:   n.ResolvedProvider,
				ProviderSchema: &providerSchema,
				State:          &state,
			},

			// Clear the diff now that we've applied it, so
			// later nodes won't see a diff that's now a no-op.
			&EvalWriteDiff{
				Addr:           addr.Resource,
				ProviderSchema: &providerSchema,
				Change:         nil,
			},

			&EvalUpdateStateHook{},
		},
	}
}

func (n *NodeApplyableResourceInstance) evalTreeManagedResource(addr addrs.AbsResourceInstance) EvalNode {
	// Declare a bunch of variables that are used for state during
	// evaluation. Most of this are written to by-address below.
	var provider providers.Interface
	var providerSchema *ProviderSchema
	var diff, diffApply *plans.ResourceInstanceChange
	var state *states.ResourceInstanceObject
	var err error
	var createNew bool
	var createBeforeDestroyEnabled bool
	var configVal cty.Value
	var deposedKey states.DeposedKey

	return &EvalSequence{
		Nodes: []EvalNode{
			&EvalGetProvider{
				Addr:   n.ResolvedProvider,
				Output: &provider,
				Schema: &providerSchema,
			},

			// Get the saved diff for apply
			&EvalReadDiff{
				Addr:           addr.Resource,
				ProviderSchema: &providerSchema,
				Change:         &diffApply,
			},

			// We don't want to do any destroys
			// (these are handled by NodeDestroyResourceInstance instead)
			&EvalIf{
				If: func(ctx EvalContext) (bool, error) {
					if diffApply == nil {
						return true, EvalEarlyExitError{}
					}
					if diffApply.Action == plans.Delete {
						return true, EvalEarlyExitError{}
					}
					return true, nil
				},
				Then: EvalNoop{},
			},

			&EvalIf{
				If: func(ctx EvalContext) (bool, error) {
					destroy := false
					if diffApply != nil {
						destroy = (diffApply.Action == plans.Delete || diffApply.Action.IsReplace())
					}
					if destroy && n.createBeforeDestroy() {
						createBeforeDestroyEnabled = true
					}
					return createBeforeDestroyEnabled, nil
				},
				Then: &EvalDeposeState{
					Addr:      addr.Resource,
					ForceKey:  n.PreallocatedDeposedKey,
					OutputKey: &deposedKey,
				},
			},

			&EvalReadState{
				Addr:           addr.Resource,
				Provider:       &provider,
				ProviderSchema: &providerSchema,

				Output: &state,
			},

			// Get the saved diff
			&EvalReadDiff{
				Addr:           addr.Resource,
				ProviderSchema: &providerSchema,
				Change:         &diff,
			},

			// Make a new diff, in case we've learned new values in the state
			// during apply which we can now incorporate.
			&EvalDiff{
				Addr:           addr.Resource,
				Config:         n.Config,
				Provider:       &provider,
				ProviderAddr:   n.ResolvedProvider,
				ProviderSchema: &providerSchema,
				State:          &state,
				PreviousDiff:   &diff,
				OutputChange:   &diffApply,
				OutputValue:    &configVal,
				OutputState:    &state,
			},

			// Compare the diffs
			&EvalCheckPlannedChange{
				Addr:           addr.Resource,
				ProviderAddr:   n.ResolvedProvider,
				ProviderSchema: &providerSchema,
				Planned:        &diff,
				Actual:         &diffApply,
			},

			&EvalGetProvider{
				Addr:   n.ResolvedProvider,
				Output: &provider,
				Schema: &providerSchema,
			},
			&EvalReadState{
				Addr:           addr.Resource,
				Provider:       &provider,
				ProviderSchema: &providerSchema,

				Output: &state,
			},

			&EvalReduceDiff{
				Addr:      addr.Resource,
				InChange:  &diffApply,
				Destroy:   false,
				OutChange: &diffApply,
			},

			// EvalReduceDiff may have simplified our planned change
			// into a NoOp if it only requires destroying, since destroying
			// is handled by NodeDestroyResourceInstance.
			&EvalIf{
				If: func(ctx EvalContext) (bool, error) {
					if diffApply == nil || diffApply.Action == plans.NoOp {
						return true, EvalEarlyExitError{}
					}
					return true, nil
				},
				Then: EvalNoop{},
			},

			// Call pre-apply hook
			&EvalApplyPre{
				Addr:   addr.Resource,
				State:  &state,
				Change: &diffApply,
			},
			&EvalApply{
				Addr:           addr.Resource,
				Config:         n.Config,
				State:          &state,
				Change:         &diffApply,
				Provider:       &provider,
				ProviderAddr:   n.ResolvedProvider,
				ProviderSchema: &providerSchema,
				Output:         &state,
				Error:          &err,
				CreateNew:      &createNew,
			},
			&EvalMaybeTainted{
				Addr:   addr.Resource,
				State:  &state,
				Change: &diffApply,
				Error:  &err,
			},
			&EvalWriteState{
				Addr:           addr.Resource,
				ProviderAddr:   n.ResolvedProvider,
				ProviderSchema: &providerSchema,
				State:          &state,
				Dependencies:   &n.Dependencies,
			},
			&EvalApplyProvisioners{
				Addr:           addr.Resource,
				State:          &state, // EvalApplyProvisioners will skip if already tainted
				ResourceConfig: n.Config,
				CreateNew:      &createNew,
				Error:          &err,
				When:           configs.ProvisionerWhenCreate,
			},
			&EvalMaybeTainted{
				Addr:   addr.Resource,
				State:  &state,
				Change: &diffApply,
				Error:  &err,
			},
			&EvalWriteState{
				Addr:           addr.Resource,
				ProviderAddr:   n.ResolvedProvider,
				ProviderSchema: &providerSchema,
				State:          &state,
				Dependencies:   &n.Dependencies,
			},
			&EvalIf{
				If: func(ctx EvalContext) (bool, error) {
					return createBeforeDestroyEnabled && err != nil, nil
				},
				Then: &EvalMaybeRestoreDeposedObject{
					Addr: addr.Resource,
					Key:  &deposedKey,
				},
			},

			// We clear the diff out here so that future nodes
			// don't see a diff that is already complete. There
			// is no longer a diff!
			&EvalIf{
				If: func(ctx EvalContext) (bool, error) {
					if !diff.Action.IsReplace() {
						return true, nil
					}
					if !n.createBeforeDestroy() {
						return true, nil
					}
					return false, nil
				},
				Then: &EvalWriteDiff{
					Addr:           addr.Resource,
					ProviderSchema: &providerSchema,
					Change:         nil,
				},
			},

			&EvalApplyPost{
				Addr:  addr.Resource,
				State: &state,
				Error: &err,
			},
			&EvalUpdateStateHook{},
		},
	}
}
