// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: BUSL-1.1

package terraform

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

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

// HookAction is an enum of actions that can be taken as a result of a hook
// callback. This allows you to modify the behavior of Terraform at runtime.
type HookAction byte

const (
	// HookActionContinue continues with processing as usual.
	HookActionContinue HookAction = iota

	// HookActionHalt halts immediately: no more hooks are processed
	// and the action that Terraform was about to take is cancelled.
	HookActionHalt
)

// HookResourceIdentity is passed to Hook interface methods to fully identify
// the resource instance being operated on. It currently includes the resource
// address and the provider address.
type HookResourceIdentity struct {
	Addr         addrs.AbsResourceInstance
	ProviderAddr addrs.Provider
}

// Hook is the interface that must be implemented to hook into various
// parts of Terraform, allowing you to inspect or change behavior at runtime.
//
// There are MANY hook points into Terraform. If you only want to implement
// some hook points, but not all (which is the likely case), then embed the
// NilHook into your struct, which implements all of the interface but does
// nothing. Then, override only the functions you want to implement.
type Hook interface {
	// PreApply and PostApply are called before and after an action for a
	// single instance is applied. The error argument in PostApply is the
	// error, if any, that was returned from the provider Apply call itself.
	PreApply(id HookResourceIdentity, dk addrs.DeposedKey, action plans.Action, priorState, plannedNewState cty.Value) (HookAction, error)
	PostApply(id HookResourceIdentity, dk addrs.DeposedKey, newState cty.Value, err error) (HookAction, error)

	// PreDiff and PostDiff are called before and after a provider is given
	// the opportunity to customize the proposed new state to produce the
	// planned new state.
	PreDiff(id HookResourceIdentity, dk addrs.DeposedKey, priorState, proposedNewState cty.Value) (HookAction, error)
	PostDiff(id HookResourceIdentity, dk addrs.DeposedKey, action plans.Action, priorState, plannedNewState cty.Value) (HookAction, error)

	// The provisioning hooks signal both the overall start end end of
	// provisioning for a particular instance and of each of the individual
	// configured provisioners for each instance. The sequence of these
	// for a given instance might look something like this:
	//
	//          PreProvisionInstance(aws_instance.foo[1], ...)
	//      PreProvisionInstanceStep(aws_instance.foo[1], "file")
	//     PostProvisionInstanceStep(aws_instance.foo[1], "file", nil)
	//      PreProvisionInstanceStep(aws_instance.foo[1], "remote-exec")
	//               ProvisionOutput(aws_instance.foo[1], "remote-exec", "Installing foo...")
	//               ProvisionOutput(aws_instance.foo[1], "remote-exec", "Configuring bar...")
	//     PostProvisionInstanceStep(aws_instance.foo[1], "remote-exec", nil)
	//         PostProvisionInstance(aws_instance.foo[1], ...)
	//
	// ProvisionOutput is called with output sent back by the provisioners.
	// This will be called multiple times as output comes in, with each call
	// representing one line of output. It cannot control whether the
	// provisioner continues running.
	PreProvisionInstance(id HookResourceIdentity, state cty.Value) (HookAction, error)
	PostProvisionInstance(id HookResourceIdentity, state cty.Value) (HookAction, error)
	PreProvisionInstanceStep(id HookResourceIdentity, typeName string) (HookAction, error)
	PostProvisionInstanceStep(id HookResourceIdentity, typeName string, err error) (HookAction, error)
	ProvisionOutput(id HookResourceIdentity, typeName string, line string)

	// PreRefresh and PostRefresh are called before and after a single
	// resource state is refreshed, respectively.
	PreRefresh(id HookResourceIdentity, dk addrs.DeposedKey, priorState cty.Value) (HookAction, error)
	PostRefresh(id HookResourceIdentity, dk addrs.DeposedKey, priorState cty.Value, newState cty.Value) (HookAction, error)

	// PreImportState and PostImportState are called before and after
	// (respectively) each state import operation for a given resource address when
	// using the legacy import command.
	PreImportState(id HookResourceIdentity, importID string) (HookAction, error)
	PostImportState(id HookResourceIdentity, imported []providers.ImportedResource) (HookAction, error)

	// PrePlanImport and PostPlanImport are called during a plan before and after planning to import
	// a new resource using the configuration-driven import workflow.
	PrePlanImport(id HookResourceIdentity, importID string) (HookAction, error)
	PostPlanImport(id HookResourceIdentity, imported []providers.ImportedResource) (HookAction, error)

	// PreApplyImport and PostApplyImport are called during an apply for each imported resource when
	// using the configuration-driven import workflow.
	PreApplyImport(id HookResourceIdentity, importing plans.ImportingSrc) (HookAction, error)
	PostApplyImport(id HookResourceIdentity, importing plans.ImportingSrc) (HookAction, error)

	// PreEphemeralOp and PostEphemeralOp are called during an operation on ephemeral resource
	// such as opening, renewal or closing
	PreEphemeralOp(id HookResourceIdentity, action plans.Action) (HookAction, error)
	PostEphemeralOp(id HookResourceIdentity, action plans.Action, opErr error) (HookAction, error)

	// Stopping is called if an external signal requests that Terraform
	// gracefully abort an operation in progress.
	//
	// This notification might suggest that the user wants Terraform to exit
	// ASAP and in that case it's possible that if Terraform runs for too much
	// longer then it'll get killed un-gracefully, and so this hook could be
	// an opportunity to persist any transient data that would be lost under
	// a subsequent kill signal. However, implementations must take care to do
	// so in a way that won't cause corruption if the process _is_ killed while
	// this hook is still running.
	//
	// This hook cannot control whether Terraform continues, because the
	// graceful shutdown process is typically already running by the time this
	// function is called.
	Stopping()

	// PostStateUpdate is called each time the state is updated. The caller must
	// coordinate a lock for the state if necessary, such that the Hook may
	// access it freely without any need for additional locks to protect from
	// concurrent writes. Implementations which modify or retain the state after
	// the call has returned must copy the state.
	PostStateUpdate(new *states.State) (HookAction, error)
}

// NilHook is a Hook implementation that does nothing. It exists only to
// simplify implementing hooks. You can embed this into your Hook implementation
// and only implement the functions you are interested in.
type NilHook struct{}

var _ Hook = (*NilHook)(nil)

func (*NilHook) PreApply(id HookResourceIdentity, dk addrs.DeposedKey, action plans.Action, priorState, plannedNewState cty.Value) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PostApply(id HookResourceIdentity, dk addrs.DeposedKey, newState cty.Value, err error) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PreDiff(id HookResourceIdentity, dk addrs.DeposedKey, priorState, proposedNewState cty.Value) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PostDiff(id HookResourceIdentity, dk addrs.DeposedKey, action plans.Action, priorState, plannedNewState cty.Value) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PreProvisionInstance(id HookResourceIdentity, state cty.Value) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PostProvisionInstance(id HookResourceIdentity, state cty.Value) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PreProvisionInstanceStep(id HookResourceIdentity, typeName string) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PostProvisionInstanceStep(id HookResourceIdentity, typeName string, err error) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) ProvisionOutput(id HookResourceIdentity, typeName string, line string) {
}

func (*NilHook) PreRefresh(id HookResourceIdentity, dk addrs.DeposedKey, priorState cty.Value) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PostRefresh(id HookResourceIdentity, dk addrs.DeposedKey, priorState cty.Value, newState cty.Value) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PreImportState(id HookResourceIdentity, importID string) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) PostImportState(id HookResourceIdentity, imported []providers.ImportedResource) (HookAction, error) {
	return HookActionContinue, nil
}

func (h *NilHook) PrePlanImport(id HookResourceIdentity, importID string) (HookAction, error) {
	return HookActionContinue, nil
}

func (h *NilHook) PostPlanImport(id HookResourceIdentity, imported []providers.ImportedResource) (HookAction, error) {
	return HookActionContinue, nil
}

func (h *NilHook) PreApplyImport(id HookResourceIdentity, importing plans.ImportingSrc) (HookAction, error) {
	return HookActionContinue, nil
}

func (h *NilHook) PostApplyImport(id HookResourceIdentity, importing plans.ImportingSrc) (HookAction, error) {
	return HookActionContinue, nil
}

func (h *NilHook) PreEphemeralOp(id HookResourceIdentity, action plans.Action) (HookAction, error) {
	return HookActionContinue, nil
}

func (h *NilHook) PostEphemeralOp(id HookResourceIdentity, action plans.Action, opErr error) (HookAction, error) {
	return HookActionContinue, nil
}

func (*NilHook) Stopping() {
	// Does nothing at all by default
}

func (*NilHook) PostStateUpdate(new *states.State) (HookAction, error) {
	return HookActionContinue, nil
}
