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
	ChecksPassing     int
	ChecksWarning     int
	ChecksCritical    int
	ExternalSources   []string
	externalSourceSet map[string]struct{} // internal to track uniqueness
}

// 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
	}

	// 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
	}

	// 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.DCSpecificRequest{}
	if done := s.parse(resp, req, &args.Datacenter, &args.QueryOptions); done {
		return nil, nil
	}

	// 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
	}

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

func summarizeServices(dump structs.NodeDump) []*ServiceSummary {
	// Collect the summary information
	var services []string
	summary := make(map[string]*ServiceSummary)
	getService := func(service string) *ServiceSummary {
		serv, ok := summary[service]
		if !ok {
			serv = &ServiceSummary{Name: service}
			summary[service] = serv
			services = append(services, service)
		}
		return serv
	}

	// Aggregate all the node information
	for _, node := range dump {
		nodeServices := make([]*ServiceSummary, len(node.Services))
		for idx, service := range node.Services {
			sum := getService(service.Service)
			sum.Tags = service.Tags
			sum.Nodes = append(sum.Nodes, node.Node)
			sum.Kind = service.Kind

			// 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(service.Meta) > 0 && service.Meta[metaExternalSource] != "" {
				source := service.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)
				}
			}

			nodeServices[idx] = sum
		}
		for _, check := range node.Checks {
			var services []*ServiceSummary
			if check.ServiceName == "" {
				services = nodeServices
			} else {
				services = []*ServiceSummary{getService(check.ServiceName)}
			}
			for _, sum := range services {
				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.Strings(services)
	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
}
