package command

import (
	"fmt"
	"strings"

	"github.com/hashicorp/terraform/backend"
	"github.com/hashicorp/terraform/command/arguments"
	"github.com/hashicorp/terraform/command/views"
	"github.com/hashicorp/terraform/tfdiags"
)

// PlanCommand is a Command implementation that compares a Terraform
// configuration to an actual infrastructure and shows the differences.
type PlanCommand struct {
	Meta
}

func (c *PlanCommand) Run(rawArgs []string) int {
	// Parse and apply global view arguments
	common, rawArgs := arguments.ParseView(rawArgs)
	c.View.Configure(common)

	// Parse and validate flags
	args, diags := arguments.ParsePlan(rawArgs)

	// Instantiate the view, even if there are flag errors, so that we render
	// diagnostics according to the desired view
	view := views.NewPlan(args.ViewType, c.RunningInAutomation, c.View)

	if diags.HasErrors() {
		view.Diagnostics(diags)
		view.HelpPrompt()
		return 1
	}

	// Check for user-supplied plugin path
	var err error
	if c.pluginPath, err = c.loadPluginPath(); err != nil {
		diags = diags.Append(err)
		view.Diagnostics(diags)
		return 1
	}

	// FIXME: the -input flag value is needed to initialize the backend and the
	// operation, but there is no clear path to pass this value down, so we
	// continue to mutate the Meta object state for now.
	c.Meta.input = args.InputEnabled

	// FIXME: the -parallelism flag is used to control the concurrency of
	// Terraform operations. At the moment, this value is used both to
	// initialize the backend via the ContextOpts field inside CLIOpts, and to
	// set a largely unused field on the Operation request. Again, there is no
	// clear path to pass this value down, so we continue to mutate the Meta
	// object state for now.
	c.Meta.parallelism = args.Operation.Parallelism

	diags = diags.Append(c.providerDevOverrideRuntimeWarnings())

	// Prepare the backend with the backend-specific arguments
	be, beDiags := c.PrepareBackend(args.State)
	diags = diags.Append(beDiags)
	if diags.HasErrors() {
		view.Diagnostics(diags)
		return 1
	}

	// Build the operation request
	opReq, opDiags := c.OperationRequest(be, view, args.Operation, args.Destroy, args.OutPath)
	diags = diags.Append(opDiags)
	if diags.HasErrors() {
		view.Diagnostics(diags)
		return 1
	}

	// Collect variable value and add them to the operation request
	diags = diags.Append(c.GatherVariables(opReq, args.Vars))
	if diags.HasErrors() {
		view.Diagnostics(diags)
		return 1
	}

	// Before we delegate to the backend, we'll print any warning diagnostics
	// we've accumulated here, since the backend will start fresh with its own
	// diagnostics.
	view.Diagnostics(diags)
	diags = nil

	// Perform the operation
	op, err := c.RunOperation(be, opReq)
	if err != nil {
		diags = diags.Append(err)
		view.Diagnostics(diags)
		return 1
	}

	if op.Result != backend.OperationSuccess {
		return op.Result.ExitStatus()
	}
	if args.DetailedExitCode && !op.PlanEmpty {
		return 2
	}

	return op.Result.ExitStatus()
}

func (c *PlanCommand) PrepareBackend(args *arguments.State) (backend.Enhanced, tfdiags.Diagnostics) {
	// FIXME: we need to apply the state arguments to the meta object here
	// because they are later used when initializing the backend. Carving a
	// path to pass these arguments to the functions that need them is
	// difficult but would make their use easier to understand.
	c.Meta.applyStateArguments(args)

	backendConfig, diags := c.loadBackendConfig(".")
	if diags.HasErrors() {
		return nil, diags
	}

	// Load the backend
	be, beDiags := c.Backend(&BackendOpts{
		Config: backendConfig,
	})
	diags = diags.Append(beDiags)
	if beDiags.HasErrors() {
		return nil, diags
	}

	return be, diags
}

func (c *PlanCommand) OperationRequest(
	be backend.Enhanced,
	view views.Plan,
	args *arguments.Operation,
	destroy bool,
	planOutPath string,
) (*backend.Operation, tfdiags.Diagnostics) {
	var diags tfdiags.Diagnostics

	// Build the operation
	opReq := c.Operation(be)
	opReq.ConfigDir = "."
	opReq.Destroy = destroy
	opReq.Hooks = view.Hooks()
	opReq.PlanRefresh = args.Refresh
	opReq.PlanOutPath = planOutPath
	opReq.Targets = args.Targets
	opReq.Type = backend.OperationTypePlan
	opReq.View = view.Operation()

	var err error
	opReq.ConfigLoader, err = c.initConfigLoader()
	if err != nil {
		diags = diags.Append(fmt.Errorf("Failed to initialize config loader: %s", err))
		return nil, diags
	}

	return opReq, diags
}

func (c *PlanCommand) GatherVariables(opReq *backend.Operation, args *arguments.Vars) tfdiags.Diagnostics {
	var diags tfdiags.Diagnostics

	// FIXME the arguments package currently trivially gathers variable related
	// arguments in a heterogenous slice, in order to minimize the number of
	// code paths gathering variables during the transition to this structure.
	// Once all commands that gather variables have been converted to this
	// structure, we could move the variable gathering code to the arguments
	// package directly, removing this shim layer.

	varArgs := args.All()
	items := make([]rawFlag, len(varArgs))
	for i := range varArgs {
		items[i].Name = varArgs[i].Name
		items[i].Value = varArgs[i].Value
	}
	c.Meta.variableArgs = rawFlags{items: &items}
	opReq.Variables, diags = c.collectVariableValues()

	return diags
}

func (c *PlanCommand) Help() string {
	helpText := `
Usage: terraform [global options] plan [options]

  Generates a speculative execution plan, showing what actions Terraform
  would take to apply the current configuration. This command will not
  actually perform the planned actions.

  You can optionally save the plan to a file, which you can then pass to
  the "apply" command to perform exactly the actions described in the plan.

Options:

  -compact-warnings   If Terraform produces any warnings that are not
                      accompanied by errors, show them in a more compact form
                      that includes only the summary messages.

  -destroy            If set, a plan will be generated to destroy all resources
                      managed by the given configuration and state.

  -detailed-exitcode  Return detailed exit codes when the command exits. This
                      will change the meaning of exit codes to:
                      0 - Succeeded, diff is empty (no changes)
                      1 - Errored
                      2 - Succeeded, there is a diff

  -input=true         Ask for input for variables if not directly set.

  -lock=true          Lock the state file when locking is supported.

  -lock-timeout=0s    Duration to retry a state lock.

  -no-color           If specified, output won't contain any color.

  -out=path           Write a plan file to the given path. This can be used as
                      input to the "apply" command.

  -parallelism=n      Limit the number of concurrent operations. Defaults to 10.

  -refresh=true       Update state prior to checking for differences.

  -state=statefile    Path to a Terraform state file to use to look
                      up Terraform-managed resources. By default it will
                      use the state "terraform.tfstate" if it exists.

  -target=resource    Resource to target. Operation will be limited to this
                      resource and its dependencies. This flag can be used
                      multiple times.

  -var 'foo=bar'      Set a variable in the Terraform configuration. This
                      flag can be set multiple times.

  -var-file=foo       Set variables in the Terraform configuration from
                      a file. If "terraform.tfvars" or any ".auto.tfvars"
                      files are present, they will be automatically loaded.
`
	return strings.TrimSpace(helpText)
}

func (c *PlanCommand) Synopsis() string {
	return "Show changes required by the current configuration"
}