package command

import (
	"fmt"
	"strings"
	"time"

	"github.com/hashicorp/nomad/api"
	"github.com/hashicorp/nomad/api/contexts"
	"github.com/posener/complete"
)

var (
	// defaultDrainDuration is the default drain duration if it is not specified
	// explicitly
	defaultDrainDuration = 1 * time.Hour
)

type NodeDrainCommand struct {
	Meta
}

func (c *NodeDrainCommand) Help() string {
	helpText := `
Usage: nomad node drain [options] <node>

  Toggles node draining on a specified node. It is required
  that either -enable or -disable is specified, but not both.
  The -self flag is useful to drain the local node.

General Options:

  ` + generalOptionsUsage() + `

Node Drain Options:

  -disable
    Disable draining for the specified node.

  -enable
    Enable draining for the specified node.

  -deadline <duration>
    Set the deadline by which all allocations must be moved off the node.
    Remaining allocations after the deadline are forced removed from the node.
    If unspecified, a default deadline of one hour is applied.

  -force
    Force remove allocations off the node immediately.

  -no-deadline
    No deadline allows the allocations to drain off the node without being force
    stopped after a certain deadline.

  -ignore-system
    Ignore system allows the drain to complete without stopping system job
    allocations.

  -self
    Set the drain status of the local node.

  -yes
    Automatic yes to prompts.
`
	return strings.TrimSpace(helpText)
}

func (c *NodeDrainCommand) Synopsis() string {
	return "Toggle drain mode on a given node"
}

func (c *NodeDrainCommand) AutocompleteFlags() complete.Flags {
	return mergeAutocompleteFlags(c.Meta.AutocompleteFlags(FlagSetClient),
		complete.Flags{
			"-disable":       complete.PredictNothing,
			"-enable":        complete.PredictNothing,
			"-deadline":      complete.PredictAnything,
			"-force":         complete.PredictNothing,
			"-no-deadline":   complete.PredictNothing,
			"-ignore-system": complete.PredictNothing,
			"-self":          complete.PredictNothing,
			"-yes":           complete.PredictNothing,
		})
}

func (c *NodeDrainCommand) AutocompleteArgs() complete.Predictor {
	return complete.PredictFunc(func(a complete.Args) []string {
		client, err := c.Meta.Client()
		if err != nil {
			return nil
		}

		resp, _, err := client.Search().PrefixSearch(a.Last, contexts.Nodes, nil)
		if err != nil {
			return []string{}
		}
		return resp.Matches[contexts.Nodes]
	})
}

func (c *NodeDrainCommand) Run(args []string) int {
	var enable, disable, force,
		noDeadline, ignoreSystem, self, autoYes bool
	var deadline string

	flags := c.Meta.FlagSet("node-drain", FlagSetClient)
	flags.Usage = func() { c.Ui.Output(c.Help()) }
	flags.BoolVar(&enable, "enable", false, "Enable drain mode")
	flags.BoolVar(&disable, "disable", false, "Disable drain mode")
	flags.StringVar(&deadline, "deadline", "", "Deadline after which allocations are force stopped")
	flags.BoolVar(&force, "force", false, "Force immediate drain")
	flags.BoolVar(&noDeadline, "no-deadline", false, "Drain node with no deadline")
	flags.BoolVar(&ignoreSystem, "ignore-system", false, "Do not drain system job allocations from the node")
	flags.BoolVar(&self, "self", false, "")
	flags.BoolVar(&autoYes, "yes", false, "Automatic yes to prompts.")

	if err := flags.Parse(args); err != nil {
		return 1
	}

	// Check that we got either enable or disable, but not both.
	if (enable && disable) || (!enable && !disable) {
		c.Ui.Error(c.Help())
		return 1
	}

	// Check that we got a node ID
	args = flags.Args()
	if l := len(args); self && l != 0 || !self && l != 1 {
		c.Ui.Error("Node ID must be specified if -self isn't being used")
		return 1
	}

	// Validate a compatible set of flags were set
	if disable && (deadline != "" || force || noDeadline || ignoreSystem) {
		c.Ui.Error("-disable can't be combined with flags configuring drain strategy")
		return 1
	}
	if deadline != "" && (force || noDeadline) {
		c.Ui.Error("-deadline can't be combined with -force or -no-deadline")
		return 1
	}
	if force && noDeadline {
		c.Ui.Error("-force and -no-deadline are mutually exclusive")
		return 1
	}

	// Parse the duration
	var d time.Duration
	if force {
		d = -1 * time.Second
	} else if noDeadline {
		d = 0
	} else if deadline != "" {
		dur, err := time.ParseDuration(deadline)
		if err != nil {
			c.Ui.Error(fmt.Sprintf("Failed to parse deadline %q: %v", deadline, err))
			return 1
		}
		if dur <= 0 {
			c.Ui.Error("A positive drain duration must be given")
			return 1
		}

		d = dur
	} else {
		d = defaultDrainDuration
	}

	// Get the HTTP client
	client, err := c.Meta.Client()
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Error initializing client: %s", err))
		return 1
	}

	// If -self flag is set then determine the current node.
	var nodeID string
	if !self {
		nodeID = args[0]
	} else {
		var err error
		if nodeID, err = getLocalNodeID(client); err != nil {
			c.Ui.Error(err.Error())
			return 1
		}
	}

	// Check if node exists
	if len(nodeID) == 1 {
		c.Ui.Error(fmt.Sprintf("Identifier must contain at least two characters."))
		return 1
	}

	nodeID = sanitizeUUIDPrefix(nodeID)
	nodes, _, err := client.Nodes().PrefixList(nodeID)
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Error toggling drain mode: %s", err))
		return 1
	}
	// Return error if no nodes are found
	if len(nodes) == 0 {
		c.Ui.Error(fmt.Sprintf("No node(s) with prefix or id %q found", nodeID))
		return 1
	}
	if len(nodes) > 1 {
		// Format the nodes list that matches the prefix so that the user
		// can create a more specific request
		out := make([]string, len(nodes)+1)
		out[0] = "ID|Datacenter|Name|Class|Drain|Status"
		for i, node := range nodes {
			out[i+1] = fmt.Sprintf("%s|%s|%s|%s|%v|%s",
				node.ID,
				node.Datacenter,
				node.Name,
				node.NodeClass,
				node.Drain,
				node.Status)
		}
		// Dump the output
		c.Ui.Error(fmt.Sprintf("Prefix matched multiple nodes\n\n%s", formatList(out)))
		return 1
	}

	// Prefix lookup matched a single node
	node, _, err := client.Nodes().Info(nodes[0].ID, nil)
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Error toggling drain mode: %s", err))
		return 1
	}

	// Confirm drain if the node was a prefix match.
	if nodeID != node.ID && !autoYes {
		verb := "enable"
		if disable {
			verb = "disable"
		}
		question := fmt.Sprintf("Are you sure you want to %s drain mode for node %q? [y/N]", verb, node.ID)
		answer, err := c.Ui.Ask(question)
		if err != nil {
			c.Ui.Error(fmt.Sprintf("Failed to parse answer: %v", err))
			return 1
		}

		if answer == "" || strings.ToLower(answer)[0] == 'n' {
			// No case
			c.Ui.Output("Canceling drain toggle")
			return 0
		} else if strings.ToLower(answer)[0] == 'y' && len(answer) > 1 {
			// Non exact match yes
			c.Ui.Output("For confirmation, an exact ‘y’ is required.")
			return 0
		} else if answer != "y" {
			c.Ui.Output("No confirmation detected. For confirmation, an exact 'y' is required.")
			return 1
		}
	}

	var spec *api.DrainSpec
	if enable {
		spec = &api.DrainSpec{
			Deadline:         d,
			IgnoreSystemJobs: ignoreSystem,
		}
	}

	// Toggle node draining
	if _, err := client.Nodes().UpdateDrain(node.ID, spec, nil); err != nil {
		c.Ui.Error(fmt.Sprintf("Error updating drain specification: %s", err))
		return 1
	}
	return 0
}