package terraform

import (
	"fmt"
	"log"

	"github.com/hashicorp/go-multierror"
	"github.com/zclconf/go-cty/cty/gocty"

	"github.com/hashicorp/terraform/addrs"
	"github.com/hashicorp/terraform/config"
	"github.com/hashicorp/terraform/configs"
	"github.com/hashicorp/terraform/tfdiags"
)

// EvalApply is an EvalNode implementation that writes the diff to
// the full diff.
type EvalApply struct {
	Addr      addrs.ResourceInstance
	State     **InstanceState
	Diff      **InstanceDiff
	Provider  *ResourceProvider
	Output    **InstanceState
	CreateNew *bool
	Error     *error
}

// TODO: test
func (n *EvalApply) Eval(ctx EvalContext) (interface{}, error) {
	diff := *n.Diff
	provider := *n.Provider
	state := *n.State

	// The provider API still expects our legacy InstanceInfo type, so we must shim it.
	legacyInfo := NewInstanceInfo(n.Addr.Absolute(ctx.Path()).ContainingResource())

	if diff.Empty() {
		log.Printf("[DEBUG] apply %s: diff is empty, so skipping.", n.Addr)
		return nil, nil
	}

	// Remove any output values from the diff
	for k, ad := range diff.CopyAttributes() {
		if ad.Type == DiffAttrOutput {
			diff.DelAttribute(k)
		}
	}

	// If the state is nil, make it non-nil
	if state == nil {
		state = new(InstanceState)
	}
	state.init()

	// Flag if we're creating a new instance
	if n.CreateNew != nil {
		*n.CreateNew = state.ID == "" && !diff.GetDestroy() || diff.RequiresNew()
	}

	// With the completed diff, apply!
	log.Printf("[DEBUG] apply %s: executing Apply", n.Addr)
	state, err := provider.Apply(legacyInfo, state, diff)
	if state == nil {
		state = new(InstanceState)
	}
	state.init()

	// Force the "id" attribute to be our ID
	if state.ID != "" {
		state.Attributes["id"] = state.ID
	}

	// If the value is the unknown variable value, then it is an error.
	// In this case we record the error and remove it from the state
	for ak, av := range state.Attributes {
		if av == config.UnknownVariableValue {
			err = multierror.Append(err, fmt.Errorf(
				"Attribute with unknown value: %s", ak))
			delete(state.Attributes, ak)
		}
	}

	// Write the final state
	if n.Output != nil {
		*n.Output = state
	}

	// If there are no errors, then we append it to our output error
	// if we have one, otherwise we just output it.
	if err != nil {
		if n.Error != nil {
			helpfulErr := fmt.Errorf("%s: %s", n.Addr, err.Error())
			*n.Error = multierror.Append(*n.Error, helpfulErr)
		} else {
			return nil, err
		}
	}

	return nil, nil
}

// EvalApplyPre is an EvalNode implementation that does the pre-Apply work
type EvalApplyPre struct {
	Addr  addrs.ResourceInstance
	State **InstanceState
	Diff  **InstanceDiff
}

// TODO: test
func (n *EvalApplyPre) Eval(ctx EvalContext) (interface{}, error) {
	state := *n.State
	diff := *n.Diff

	// The hook API still uses our legacy InstanceInfo type, so we must
	// shim it.
	legacyInfo := NewInstanceInfo(n.Addr.ContainingResource().Absolute(ctx.Path()))

	// If the state is nil, make it non-nil
	if state == nil {
		state = new(InstanceState)
	}
	state.init()

	if resourceHasUserVisibleApply(legacyInfo) {
		// Call post-apply hook
		err := ctx.Hook(func(h Hook) (HookAction, error) {
			return h.PreApply(legacyInfo, state, diff)
		})
		if err != nil {
			return nil, err
		}
	}

	return nil, nil
}

// EvalApplyPost is an EvalNode implementation that does the post-Apply work
type EvalApplyPost struct {
	Addr  addrs.ResourceInstance
	State **InstanceState
	Error *error
}

// TODO: test
func (n *EvalApplyPost) Eval(ctx EvalContext) (interface{}, error) {
	state := *n.State

	// The hook API still uses our legacy InstanceInfo type, so we must
	// shim it.
	legacyInfo := NewInstanceInfo(n.Addr.ContainingResource().Absolute(ctx.Path()))

	if resourceHasUserVisibleApply(legacyInfo) {
		// Call post-apply hook
		err := ctx.Hook(func(h Hook) (HookAction, error) {
			return h.PostApply(legacyInfo, state, *n.Error)
		})
		if err != nil {
			return nil, err
		}
	}

	return nil, *n.Error
}

// resourceHasUserVisibleApply returns true if the given resource is one where
// apply actions should be exposed to the user.
//
// Certain resources do apply actions only as an implementation detail, so
// these should not be advertised to code outside of this package.
func resourceHasUserVisibleApply(info *InstanceInfo) bool {
	addr := info.ResourceAddress()

	// Only managed resources have user-visible apply actions.
	// In particular, this excludes data resources since we "apply" these
	// only as an implementation detail of removing them from state when
	// they are destroyed. (When reading, they don't get here at all because
	// we present them as "Refresh" actions.)
	return addr.Mode == config.ManagedResourceMode
}

// EvalApplyProvisioners is an EvalNode implementation that executes
// the provisioners for a resource.
//
// TODO(mitchellh): This should probably be split up into a more fine-grained
// ApplyProvisioner (single) that is looped over.
type EvalApplyProvisioners struct {
	Addr           addrs.ResourceInstance
	State          **InstanceState
	ResourceConfig *configs.Resource
	CreateNew      *bool
	Error          *error

	// When is the type of provisioner to run at this point
	When configs.ProvisionerWhen
}

// TODO: test
func (n *EvalApplyProvisioners) Eval(ctx EvalContext) (interface{}, error) {
	state := *n.State

	// The hook API still uses the legacy InstanceInfo type, so we need to shim it.
	legacyInfo := NewInstanceInfo(n.Addr.Resource.Absolute(ctx.Path()))

	if n.CreateNew != nil && !*n.CreateNew {
		// If we're not creating a new resource, then don't run provisioners
		return nil, nil
	}

	provs := n.filterProvisioners()
	if len(provs) == 0 {
		// We have no provisioners, so don't do anything
		return nil, nil
	}

	// taint tells us whether to enable tainting.
	taint := n.When == configs.ProvisionerWhenCreate

	if n.Error != nil && *n.Error != nil {
		if taint {
			state.Tainted = true
		}

		// We're already tainted, so just return out
		return nil, nil
	}

	{
		// Call pre hook
		err := ctx.Hook(func(h Hook) (HookAction, error) {
			return h.PreProvisionResource(legacyInfo, state)
		})
		if err != nil {
			return nil, err
		}
	}

	// If there are no errors, then we append it to our output error
	// if we have one, otherwise we just output it.
	err := n.apply(ctx, provs)
	if err != nil {
		if taint {
			state.Tainted = true
		}

		*n.Error = multierror.Append(*n.Error, err)
		return nil, err
	}

	{
		// Call post hook
		err := ctx.Hook(func(h Hook) (HookAction, error) {
			return h.PostProvisionResource(legacyInfo, state)
		})
		if err != nil {
			return nil, err
		}
	}

	return nil, nil
}

// filterProvisioners filters the provisioners on the resource to only
// the provisioners specified by the "when" option.
func (n *EvalApplyProvisioners) filterProvisioners() []*configs.Provisioner {
	// Fast path the zero case
	if n.ResourceConfig == nil || n.ResourceConfig.Managed == nil {
		return nil
	}

	if len(n.ResourceConfig.Managed.Provisioners) == 0 {
		return nil
	}

	result := make([]*configs.Provisioner, 0, len(n.ResourceConfig.Managed.Provisioners))
	for _, p := range n.ResourceConfig.Managed.Provisioners {
		if p.When == n.When {
			result = append(result, p)
		}
	}

	return result
}

func (n *EvalApplyProvisioners) apply(ctx EvalContext, provs []*configs.Provisioner) error {
	instanceAddr := n.Addr
	state := *n.State

	// The hook API still uses the legacy InstanceInfo type, so we need to shim it.
	legacyInfo := NewInstanceInfo(n.Addr.Resource.Absolute(ctx.Path()))

	// Store the original connection info, restore later
	origConnInfo := state.Ephemeral.ConnInfo
	defer func() {
		state.Ephemeral.ConnInfo = origConnInfo
	}()

	var diags tfdiags.Diagnostics

	for _, prov := range provs {
		// Get the provisioner
		provisioner := ctx.Provisioner(prov.Type)
		schema := ctx.ProvisionerSchema(prov.Type)

		// Evaluate the main provisioner configuration.
		config, _, configDiags := ctx.EvaluateBlock(prov.Config, schema, instanceAddr)
		diags = diags.Append(configDiags)

		connInfo, _, connInfoDiags := ctx.EvaluateBlock(prov.Config, connectionBlockSupersetSchema, instanceAddr)
		diags = diags.Append(connInfoDiags)

		if configDiags.HasErrors() || connInfoDiags.HasErrors() {
			continue
		}

		// Merge the connection information, and also lower everything to strings
		// for compatibility with the communicator API.
		overlay := make(map[string]string)
		if origConnInfo != nil {
			for k, v := range origConnInfo {
				overlay[k] = v
			}
		}
		for it := connInfo.ElementIterator(); it.Next(); {
			kv, vv := it.Element()
			var k, v string

			err := gocty.FromCtyValue(kv, &k)
			if err != nil {
				// Should never happen, because connectionBlockSupersetSchema requires all primitives
				panic(err)
			}
			err = gocty.FromCtyValue(vv, &v)
			if err != nil {
				// Should never happen, because connectionBlockSupersetSchema requires all primitives
				panic(err)
			}

			overlay[k] = v
		}
		state.Ephemeral.ConnInfo = overlay

		{
			// Call pre hook
			err := ctx.Hook(func(h Hook) (HookAction, error) {
				return h.PreProvision(legacyInfo, prov.Type)
			})
			if err != nil {
				return err
			}
		}

		// The output function
		outputFn := func(msg string) {
			ctx.Hook(func(h Hook) (HookAction, error) {
				h.ProvisionOutput(legacyInfo, prov.Type, msg)
				return HookActionContinue, nil
			})
		}

		// The provisioner API still uses our legacy ResourceConfig type, so
		// we need to shim it.
		legacyRC := NewResourceConfigShimmed(config, schema)

		// Invoke the Provisioner
		output := CallbackUIOutput{OutputFn: outputFn}
		applyErr := provisioner.Apply(&output, state, legacyRC)

		// Call post hook
		hookErr := ctx.Hook(func(h Hook) (HookAction, error) {
			return h.PostProvision(legacyInfo, prov.Type, applyErr)
		})

		// Handle the error before we deal with the hook
		if applyErr != nil {
			// Determine failure behavior
			switch prov.OnFailure {
			case configs.ProvisionerOnFailureContinue:
				log.Printf("[INFO] apply %s [%s]: error during provision, but continuing as requested in configuration", n.Addr, prov.Type)
			case configs.ProvisionerOnFailureFail:
				return applyErr
			}
		}

		// Deal with the hook
		if hookErr != nil {
			return hookErr
		}
	}

	return diags.ErrWithWarnings()
}