package nomad

import (
	"fmt"
	"time"

	"github.com/armon/go-metrics"
	"github.com/hashicorp/nomad/nomad/structs"
)

// Client endpoint is used for client interactions
type Client struct {
	srv *Server
}

// Register is used to upsert a client that is available for scheduling
func (c *Client) Register(args *structs.NodeRegisterRequest, reply *structs.NodeUpdateResponse) error {
	if done, err := c.srv.forward("Client.Register", args, args, reply); done {
		return err
	}
	defer metrics.MeasureSince([]string{"nomad", "client", "register"}, time.Now())

	// Validate the arguments
	if args.Node == nil {
		return fmt.Errorf("missing node for client registration")
	}
	if args.Node.ID == "" {
		return fmt.Errorf("missing node ID for client registration")
	}
	if args.Node.Datacenter == "" {
		return fmt.Errorf("missing datacenter for client registration")
	}
	if args.Node.Name == "" {
		return fmt.Errorf("missing node name for client registration")
	}

	// Default the status if none is given
	if args.Node.Status == "" {
		args.Node.Status = structs.NodeStatusInit
	}
	if !structs.ValidNodeStatus(args.Node.Status) {
		return fmt.Errorf("invalid status for node")
	}

	// Commit this update via Raft
	_, index, err := c.srv.raftApply(structs.NodeRegisterRequestType, args)
	if err != nil {
		c.srv.logger.Printf("[ERR] nomad.client: Register failed: %v", err)
		return err
	}
	reply.NodeModifyIndex = index

	// Check if we should trigger evaluations
	if structs.ShouldDrainNode(args.Node.Status) {
		evalIDs, evalIndex, err := c.createNodeEvals(args.Node.ID, index)
		if err != nil {
			c.srv.logger.Printf("[ERR] nomad.client: eval creation failed: %v", err)
			return err
		}
		reply.EvalIDs = evalIDs
		reply.EvalCreateIndex = evalIndex
	}

	// Set the reply index
	reply.Index = index
	return nil
}

// Deregister is used to remove a client from the client. If a client should
// just be made unavailable for scheduling, a status update is prefered.
func (c *Client) Deregister(args *structs.NodeDeregisterRequest, reply *structs.NodeUpdateResponse) error {
	if done, err := c.srv.forward("Client.Deregister", args, args, reply); done {
		return err
	}
	defer metrics.MeasureSince([]string{"nomad", "client", "deregister"}, time.Now())

	// Verify the arguments
	if args.NodeID == "" {
		return fmt.Errorf("missing node ID for client deregistration")
	}

	// Commit this update via Raft
	_, index, err := c.srv.raftApply(structs.NodeDeregisterRequestType, args)
	if err != nil {
		c.srv.logger.Printf("[ERR] nomad.client: Deregister failed: %v", err)
		return err
	}

	// Create the evaluations for this node
	evalIDs, evalIndex, err := c.createNodeEvals(args.NodeID, index)
	if err != nil {
		c.srv.logger.Printf("[ERR] nomad.client: eval creation failed: %v", err)
		return err
	}

	// Setup the reply
	reply.EvalIDs = evalIDs
	reply.EvalCreateIndex = evalIndex
	reply.NodeModifyIndex = index
	reply.Index = index
	return nil
}

// UpdateStatus is used to update the status of a client node
func (c *Client) UpdateStatus(args *structs.NodeUpdateStatusRequest, reply *structs.NodeUpdateResponse) error {
	if done, err := c.srv.forward("Client.UpdateStatus", args, args, reply); done {
		return err
	}
	defer metrics.MeasureSince([]string{"nomad", "client", "update_status"}, time.Now())

	// Verify the arguments
	if args.NodeID == "" {
		return fmt.Errorf("missing node ID for client deregistration")
	}
	if !structs.ValidNodeStatus(args.Status) {
		return fmt.Errorf("invalid status for node")
	}

	// Commit this update via Raft
	_, index, err := c.srv.raftApply(structs.NodeUpdateStatusRequestType, args)
	if err != nil {
		c.srv.logger.Printf("[ERR] nomad.client: status update failed: %v", err)
		return err
	}
	reply.NodeModifyIndex = index

	// Check if we should trigger evaluations
	if structs.ShouldDrainNode(args.Status) {
		evalIDs, evalIndex, err := c.createNodeEvals(args.NodeID, index)
		if err != nil {
			c.srv.logger.Printf("[ERR] nomad.client: eval creation failed: %v", err)
			return err
		}
		reply.EvalIDs = evalIDs
		reply.EvalCreateIndex = evalIndex
	}

	// Set the reply index
	reply.Index = index
	return nil
}

// GetNode is used to request information about a specific ndoe
func (c *Client) GetNode(args *structs.NodeSpecificRequest,
	reply *structs.SingleNodeResponse) error {
	if done, err := c.srv.forward("Client.GetNode", args, args, reply); done {
		return err
	}
	defer metrics.MeasureSince([]string{"nomad", "client", "get_node"}, time.Now())

	// Verify the arguments
	if args.NodeID == "" {
		return fmt.Errorf("missing node ID")
	}

	// Look for the node
	snap, err := c.srv.fsm.State().Snapshot()
	if err != nil {
		return err
	}
	out, err := snap.GetNodeByID(args.NodeID)
	if err != nil {
		return err
	}

	// Setup the output
	if out != nil {
		reply.Node = out
		reply.Index = out.ModifyIndex
	} else {
		// Use the last index that affected the nodes table
		index, err := snap.GetIndex("nodes")
		if err != nil {
			return err
		}
		reply.Index = index
	}

	// Set the query response
	c.srv.setQueryMeta(&reply.QueryMeta)
	return nil
}

// createNodeEvals is used to create evaluations for each alloc on a node.
// Each Eval is scoped to a job, so we need to potentially trigger many evals.
func (c *Client) createNodeEvals(nodeID string, nodeIndex uint64) ([]string, uint64, error) {
	// Snapshot the state
	snap, err := c.srv.fsm.State().Snapshot()
	if err != nil {
		return nil, 0, fmt.Errorf("failed to snapshot state: %v", err)
	}

	// Find all the allocations for this node
	allocs, err := snap.AllocsByNode(nodeID)
	if err != nil {
		return nil, 0, fmt.Errorf("failed to find allocs for '%s': %v", nodeID, err)
	}

	// Fast-path if nothing to do
	if len(allocs) == 0 {
		return nil, 0, nil
	}

	// Create an eval for each JobID affected
	var evals []*structs.Evaluation
	var evalIDs []string
	jobIDs := make(map[string]struct{})

	for _, alloc := range allocs {
		// Deduplicate on JobID
		if _, ok := jobIDs[alloc.JobID]; ok {
			continue
		}
		jobIDs[alloc.JobID] = struct{}{}

		// Create a new eval
		eval := &structs.Evaluation{
			ID:              generateUUID(),
			Priority:        alloc.Job.Priority,
			Type:            alloc.Job.Type,
			TriggeredBy:     structs.EvalTriggerNodeUpdate,
			JobID:           alloc.JobID,
			NodeID:          nodeID,
			NodeModifyIndex: nodeIndex,
			Status:          structs.EvalStatusPending,
		}
		evals = append(evals, eval)
		evalIDs = append(evalIDs, eval.ID)
	}

	// Create the Raft transaction
	update := &structs.EvalUpdateRequest{
		Evals:        evals,
		WriteRequest: structs.WriteRequest{Region: c.srv.config.Region},
	}

	// Commit this evaluation via Raft
	_, evalIndex, err := c.srv.raftApply(structs.EvalUpdateRequestType, update)
	if err != nil {
		return nil, 0, err
	}
	return evalIDs, evalIndex, nil
}