package agent

import (
	"fmt"
	"net/http"
	"sort"
	"strings"

	"github.com/hashicorp/consul/agent/structs"
	"github.com/hashicorp/consul/api"
)

// metaExternalSource is the key name for the service instance meta that
// defines the external syncing source. This is used by the UI APIs below
// to extract this.
const metaExternalSource = "external-source"

// ServiceSummary is used to summarize a service
type ServiceSummary struct {
	Kind              structs.ServiceKind `json:",omitempty"`
	Name              string
	Tags              []string
	Nodes             []string
	InstanceCount     int
	ChecksPassing     int
	ChecksWarning     int
	ChecksCritical    int
	ExternalSources   []string
	externalSourceSet map[string]struct{} // internal to track uniqueness

	structs.EnterpriseMeta
}

// UINodes is used to list the nodes in a given datacenter. We return a
// NodeDump which provides overview information for all the nodes
func (s *HTTPServer) UINodes(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
	// Parse arguments
	args := structs.DCSpecificRequest{}
	if done := s.parse(resp, req, &args.Datacenter, &args.QueryOptions); done {
		return nil, nil
	}

	if err := s.parseEntMeta(req, &args.EnterpriseMeta); err != nil {
		return nil, err
	}

	s.parseFilter(req, &args.Filter)

	// Make the RPC request
	var out structs.IndexedNodeDump
	defer setMeta(resp, &out.QueryMeta)
RPC:
	if err := s.agent.RPC("Internal.NodeDump", &args, &out); err != nil {
		// Retry the request allowing stale data if no leader
		if strings.Contains(err.Error(), structs.ErrNoLeader.Error()) && !args.AllowStale {
			args.AllowStale = true
			goto RPC
		}
		return nil, err
	}

	// Use empty list instead of nil
	for _, info := range out.Dump {
		if info.Services == nil {
			info.Services = make([]*structs.NodeService, 0)
		}
		if info.Checks == nil {
			info.Checks = make([]*structs.HealthCheck, 0)
		}
	}
	if out.Dump == nil {
		out.Dump = make(structs.NodeDump, 0)
	}
	return out.Dump, nil
}

// UINodeInfo is used to get info on a single node in a given datacenter. We return a
// NodeInfo which provides overview information for the node
func (s *HTTPServer) UINodeInfo(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
	// Parse arguments
	args := structs.NodeSpecificRequest{}
	if done := s.parse(resp, req, &args.Datacenter, &args.QueryOptions); done {
		return nil, nil
	}

	if err := s.parseEntMeta(req, &args.EnterpriseMeta); err != nil {
		return nil, err
	}

	// Verify we have some DC, or use the default
	args.Node = strings.TrimPrefix(req.URL.Path, "/v1/internal/ui/node/")
	if args.Node == "" {
		resp.WriteHeader(http.StatusBadRequest)
		fmt.Fprint(resp, "Missing node name")
		return nil, nil
	}

	// Make the RPC request
	var out structs.IndexedNodeDump
	defer setMeta(resp, &out.QueryMeta)
RPC:
	if err := s.agent.RPC("Internal.NodeInfo", &args, &out); err != nil {
		// Retry the request allowing stale data if no leader
		if strings.Contains(err.Error(), structs.ErrNoLeader.Error()) && !args.AllowStale {
			args.AllowStale = true
			goto RPC
		}
		return nil, err
	}

	// Return only the first entry
	if len(out.Dump) > 0 {
		info := out.Dump[0]
		if info.Services == nil {
			info.Services = make([]*structs.NodeService, 0)
		}
		if info.Checks == nil {
			info.Checks = make([]*structs.HealthCheck, 0)
		}
		return info, nil
	}

	resp.WriteHeader(http.StatusNotFound)
	return nil, nil
}

// UIServices is used to list the services in a given datacenter. We return a
// ServiceSummary which provides overview information for the service
func (s *HTTPServer) UIServices(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
	// Parse arguments
	args := structs.ServiceDumpRequest{}
	if done := s.parse(resp, req, &args.Datacenter, &args.QueryOptions); done {
		return nil, nil
	}

	if err := s.parseEntMeta(req, &args.EnterpriseMeta); err != nil {
		return nil, err
	}

	s.parseFilter(req, &args.Filter)

	// Make the RPC request
	var out structs.IndexedCheckServiceNodes
	defer setMeta(resp, &out.QueryMeta)
RPC:
	if err := s.agent.RPC("Internal.ServiceDump", &args, &out); err != nil {
		// Retry the request allowing stale data if no leader
		if strings.Contains(err.Error(), structs.ErrNoLeader.Error()) && !args.AllowStale {
			args.AllowStale = true
			goto RPC
		}
		return nil, err
	}

	// Generate the summary
	return summarizeServices(out.Nodes), nil
}

func summarizeServices(dump structs.CheckServiceNodes) []*ServiceSummary {
	// Collect the summary information
	var services []structs.ServiceID
	summary := make(map[structs.ServiceID]*ServiceSummary)
	getService := func(service structs.ServiceID) *ServiceSummary {
		serv, ok := summary[service]
		if !ok {
			serv = &ServiceSummary{
				Name:           service.ID,
				EnterpriseMeta: service.EnterpriseMeta,
				// the other code will increment this unconditionally so we
				// shouldn't initialize it to 1
				InstanceCount: 0,
			}
			summary[service] = serv
			services = append(services, service)
		}
		return serv
	}

	var sid structs.ServiceID
	for _, csn := range dump {
		svc := csn.Service
		sid.Init(svc.Service, &svc.EnterpriseMeta)
		sum := getService(sid)
		sum.Nodes = append(sum.Nodes, csn.Node.Node)
		sum.Kind = svc.Kind
		sum.InstanceCount += 1
		for _, tag := range svc.Tags {
			found := false
			for _, existing := range sum.Tags {
				if existing == tag {
					found = true
					break
				}
			}

			if !found {
				sum.Tags = append(sum.Tags, tag)
			}
		}

		// If there is an external source, add it to the list of external
		// sources. We only want to add unique sources so there is extra
		// accounting here with an unexported field to maintain the set
		// of sources.
		if len(svc.Meta) > 0 && svc.Meta[metaExternalSource] != "" {
			source := svc.Meta[metaExternalSource]
			if sum.externalSourceSet == nil {
				sum.externalSourceSet = make(map[string]struct{})
			}
			if _, ok := sum.externalSourceSet[source]; !ok {
				sum.externalSourceSet[source] = struct{}{}
				sum.ExternalSources = append(sum.ExternalSources, source)
			}
		}

		for _, check := range csn.Checks {
			switch check.Status {
			case api.HealthPassing:
				sum.ChecksPassing++
			case api.HealthWarning:
				sum.ChecksWarning++
			case api.HealthCritical:
				sum.ChecksCritical++
			}
		}
	}

	// Return the services in sorted order
	sort.Slice(services, func(i, j int) bool {
		return services[i].LessThan(&services[j])
	})
	output := make([]*ServiceSummary, len(summary))
	for idx, service := range services {
		// Sort the nodes
		sum := summary[service]
		sort.Strings(sum.Nodes)
		output[idx] = sum
	}
	return output
}