package remote

import (
	"bufio"
	"context"
	"fmt"
	"io"
	"log"

	tfe "github.com/hashicorp/go-tfe"
	version "github.com/hashicorp/go-version"
	"github.com/hashicorp/terraform/backend"
	"github.com/hashicorp/terraform/plans"
	"github.com/hashicorp/terraform/terraform"
	"github.com/hashicorp/terraform/tfdiags"
)

func (b *Remote) opApply(stopCtx, cancelCtx context.Context, op *backend.Operation, w *tfe.Workspace) (*tfe.Run, error) {
	log.Printf("[INFO] backend/remote: starting Apply operation")

	var diags tfdiags.Diagnostics

	// We should remove the `CanUpdate` part of this test, but for now
	// (to remain compatible with tfe.v2.1) we'll leave it in here.
	if !w.Permissions.CanUpdate && !w.Permissions.CanQueueApply {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"Insufficient rights to apply changes",
			"The provided credentials have insufficient rights to apply changes. In order "+
				"to apply changes at least write permissions on the workspace are required.",
		))
		return nil, diags.Err()
	}

	if w.VCSRepo != nil {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"Apply not allowed for workspaces with a VCS connection",
			"A workspace that is connected to a VCS requires the VCS-driven workflow "+
				"to ensure that the VCS remains the single source of truth.",
		))
		return nil, diags.Err()
	}

	if op.Parallelism != defaultParallelism {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"Custom parallelism values are currently not supported",
			`The "remote" backend does not support setting a custom parallelism `+
				`value at this time.`,
		))
	}

	if op.PlanFile != nil {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"Applying a saved plan is currently not supported",
			`The "remote" backend currently requires configuration to be present and `+
				`does not accept an existing saved plan as an argument at this time.`,
		))
	}

	if !op.PlanRefresh {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"Applying without refresh is currently not supported",
			`Currently the "remote" backend will always do an in-memory refresh of `+
				`the Terraform state prior to generating the plan.`,
		))
	}

	if b.hasExplicitVariableValues(op) {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"Run variables are currently not supported",
			fmt.Sprintf(
				"The \"remote\" backend does not support setting run variables at this time. "+
					"Currently the only to way to pass variables to the remote backend is by "+
					"creating a '*.auto.tfvars' variables file. This file will automatically "+
					"be loaded by the \"remote\" backend when the workspace is configured to use "+
					"Terraform v0.10.0 or later.\n\nAdditionally you can also set variables on "+
					"the workspace in the web UI:\nhttps://%s/app/%s/%s/variables",
				b.hostname, b.organization, op.Workspace,
			),
		))
	}

	if !op.HasConfig() && op.PlanMode != plans.DestroyMode {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"No configuration files found",
			`Apply requires configuration to be present. Applying without a configuration `+
				`would mark everything for destruction, which is normally not what is desired. `+
				`If you would like to destroy everything, please run 'terraform destroy' which `+
				`does not require any configuration files.`,
		))
	}

	if len(op.Targets) != 0 {
		// For API versions prior to 2.3, RemoteAPIVersion will return an empty string,
		// so if there's an error when parsing the RemoteAPIVersion, it's handled as
		// equivalent to an API version < 2.3.
		currentAPIVersion, parseErr := version.NewVersion(b.client.RemoteAPIVersion())
		desiredAPIVersion, _ := version.NewVersion("2.3")

		if parseErr != nil || currentAPIVersion.LessThan(desiredAPIVersion) {
			diags = diags.Append(tfdiags.Sourceless(
				tfdiags.Error,
				"Resource targeting is not supported",
				fmt.Sprintf(
					`The host %s does not support the -target option for `+
						`remote plans.`,
					b.hostname,
				),
			))
		}
	}

	// Return if there are any errors.
	if diags.HasErrors() {
		return nil, diags.Err()
	}

	// Run the plan phase.
	r, err := b.plan(stopCtx, cancelCtx, op, w)
	if err != nil {
		return r, err
	}

	// This check is also performed in the plan method to determine if
	// the policies should be checked, but we need to check the values
	// here again to determine if we are done and should return.
	if !r.HasChanges || r.Status == tfe.RunCanceled || r.Status == tfe.RunErrored {
		return r, nil
	}

	// Retrieve the run to get its current status.
	r, err = b.client.Runs.Read(stopCtx, r.ID)
	if err != nil {
		return r, generalError("Failed to retrieve run", err)
	}

	// Return if the run cannot be confirmed.
	if !w.AutoApply && !r.Actions.IsConfirmable {
		return r, nil
	}

	// Since we already checked the permissions before creating the run
	// this should never happen. But it doesn't hurt to keep this in as
	// a safeguard for any unexpected situations.
	if !w.AutoApply && !r.Permissions.CanApply {
		// Make sure we discard the run if possible.
		if r.Actions.IsDiscardable {
			err = b.client.Runs.Discard(stopCtx, r.ID, tfe.RunDiscardOptions{})
			if err != nil {
				switch op.PlanMode {
				case plans.DestroyMode:
					return r, generalError("Failed to discard destroy", err)
				default:
					return r, generalError("Failed to discard apply", err)
				}
			}
		}
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			"Insufficient rights to approve the pending changes",
			fmt.Sprintf("There are pending changes, but the provided credentials have "+
				"insufficient rights to approve them. The run will be discarded to prevent "+
				"it from blocking the queue waiting for external approval. To queue a run "+
				"that can be approved by someone else, please use the 'Queue Plan' button in "+
				"the web UI:\nhttps://%s/app/%s/%s/runs", b.hostname, b.organization, op.Workspace),
		))
		return r, diags.Err()
	}

	mustConfirm := (op.UIIn != nil && op.UIOut != nil) && !op.AutoApprove

	if !w.AutoApply {
		if mustConfirm {
			opts := &terraform.InputOpts{Id: "approve"}

			if op.PlanMode == plans.DestroyMode {
				opts.Query = "\nDo you really want to destroy all resources in workspace \"" + op.Workspace + "\"?"
				opts.Description = "Terraform will destroy all your managed infrastructure, as shown above.\n" +
					"There is no undo. Only 'yes' will be accepted to confirm."
			} else {
				opts.Query = "\nDo you want to perform these actions in workspace \"" + op.Workspace + "\"?"
				opts.Description = "Terraform will perform the actions described above.\n" +
					"Only 'yes' will be accepted to approve."
			}

			err = b.confirm(stopCtx, op, opts, r, "yes")
			if err != nil && err != errRunApproved {
				return r, err
			}
		}

		if err != errRunApproved {
			if err = b.client.Runs.Apply(stopCtx, r.ID, tfe.RunApplyOptions{}); err != nil {
				return r, generalError("Failed to approve the apply command", err)
			}
		}
	}

	// If we don't need to ask for confirmation, insert a blank
	// line to separate the ouputs.
	if w.AutoApply || !mustConfirm {
		if b.CLI != nil {
			b.CLI.Output("")
		}
	}

	r, err = b.waitForRun(stopCtx, cancelCtx, op, "apply", r, w)
	if err != nil {
		return r, err
	}

	logs, err := b.client.Applies.Logs(stopCtx, r.Apply.ID)
	if err != nil {
		return r, generalError("Failed to retrieve logs", err)
	}
	reader := bufio.NewReaderSize(logs, 64*1024)

	if b.CLI != nil {
		skip := 0
		for next := true; next; {
			var l, line []byte

			for isPrefix := true; isPrefix; {
				l, isPrefix, err = reader.ReadLine()
				if err != nil {
					if err != io.EOF {
						return r, generalError("Failed to read logs", err)
					}
					next = false
				}
				line = append(line, l...)
			}

			// Skip the first 3 lines to prevent duplicate output.
			if skip < 3 {
				skip++
				continue
			}

			if next || len(line) > 0 {
				b.CLI.Output(b.Colorize().Color(string(line)))
			}
		}
	}

	return r, nil
}

const applyDefaultHeader = `
[reset][yellow]Running apply in the remote backend. Output will stream here. Pressing Ctrl-C
will cancel the remote apply if it's still pending. If the apply started it
will stop streaming the logs, but will not stop the apply running remotely.[reset]

Preparing the remote apply...
`
