package agent

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

	"github.com/hashicorp/consul/agent/config"
	"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"

type GatewayConfig struct {
	AssociatedServiceCount int      `json:",omitempty"`
	Addresses              []string `json:",omitempty"`
	// internal to track uniqueness
	addressesSet map[string]struct{}
}

// 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
	GatewayConfig        GatewayConfig       `json:",omitempty"`
	ConnectedWithProxy   bool
	ConnectedWithGateway bool

	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.IndexedNodesWithGateways
	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
	// TODO (gateways) (freddy) Have Internal.ServiceDump return ServiceDump instead. Need to add bexpr filtering for type.
	return summarizeServices(out.Nodes.ToServiceDump(), out.Gateways, s.agent.config), nil
}

// UIGatewayServices is used to query all the nodes for services associated with a gateway along with their gateway config
func (s *HTTPServer) UIGatewayServicesNodes(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
	// Parse arguments
	args := structs.ServiceSpecificRequest{}
	if err := s.parseEntMetaNoWildcard(req, &args.EnterpriseMeta); err != nil {
		return nil, err
	}
	if done := s.parse(resp, req, &args.Datacenter, &args.QueryOptions); done {
		return nil, nil
	}

	// Pull out the service name
	args.ServiceName = strings.TrimPrefix(req.URL.Path, "/v1/internal/ui/gateway-services-nodes/")
	if args.ServiceName == "" {
		resp.WriteHeader(http.StatusBadRequest)
		fmt.Fprint(resp, "Missing gateway name")
		return nil, nil
	}

	// Make the RPC request
	var out structs.IndexedServiceDump
	defer setMeta(resp, &out.QueryMeta)
RPC:
	if err := s.agent.RPC("Internal.GatewayServiceDump", &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 summarizeServices(out.Dump, nil, s.agent.config), nil
}

func summarizeServices(dump structs.ServiceDump, gateways structs.GatewayServices, cfg *config.RuntimeConfig) []*ServiceSummary {
	// Collect the summary information
	var services []structs.ServiceName
	summary := make(map[structs.ServiceName]*ServiceSummary)

	linkedGateways := make(map[structs.ServiceName][]structs.ServiceName)
	hasProxy := make(map[structs.ServiceName]bool)

	getService := func(service structs.ServiceName) *ServiceSummary {
		serv, ok := summary[service]
		if !ok {
			serv = &ServiceSummary{
				Name:           service.Name,
				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
	}

	// Collect the list of services linked to each gateway up front
	// THis also allows tracking whether a service name is associated with a gateway
	gsCount := make(map[structs.ServiceName]int)

	for _, gs := range gateways {
		gsCount[gs.Gateway] += 1
		linkedGateways[gs.Service] = append(linkedGateways[gs.Service], gs.Gateway)
	}

	for _, csn := range dump {
		if csn.GatewayService != nil {
			gwsvc := csn.GatewayService
			sum := getService(gwsvc.Service)
			modifySummaryForGatewayService(cfg, sum, gwsvc)
		}

		// Will happen in cases where we only have the GatewayServices mapping
		if csn.Service == nil {
			continue
		}
		sid := structs.NewServiceName(csn.Service.Service, &csn.Service.EnterpriseMeta)
		sum := getService(sid)

		svc := csn.Service
		sum.Nodes = append(sum.Nodes, csn.Node.Node)
		sum.Kind = svc.Kind
		sum.InstanceCount += 1
		if svc.Kind == structs.ServiceKindConnectProxy {
			hasProxy[structs.NewServiceName(svc.Proxy.DestinationServiceName, &svc.EnterpriseMeta)] = true
		}
		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 {
		sum := summary[service]
		if hasProxy[service] {
			sum.ConnectedWithProxy = true
		}

		// Verify that at least one of the gateways linked by config entry has an instance registered in the catalog
		for _, gw := range linkedGateways[service] {
			if s := summary[gw]; s != nil && s.InstanceCount > 0 {
				sum.ConnectedWithGateway = true
			}
		}
		sum.GatewayConfig.AssociatedServiceCount = gsCount[service]

		// Sort the nodes and tags
		sort.Strings(sum.Nodes)
		sort.Strings(sum.Tags)
		output[idx] = sum
	}
	return output
}

func modifySummaryForGatewayService(
	cfg *config.RuntimeConfig,
	sum *ServiceSummary,
	gwsvc *structs.GatewayService,
) {
	var dnsAddresses []string
	for _, domain := range []string{cfg.DNSDomain, cfg.DNSAltDomain} {
		// If the domain is empty, do not use it to construct a valid DNS
		// address
		if domain == "" {
			continue
		}
		dnsAddresses = append(dnsAddresses, serviceIngressDNSName(
			gwsvc.Service.Name,
			cfg.Datacenter,
			domain,
			&gwsvc.Service.EnterpriseMeta,
		))
	}

	for _, addr := range gwsvc.Addresses(dnsAddresses) {
		// check for duplicates, a service will have a ServiceInfo struct for
		// every instance that is registered.
		if _, ok := sum.GatewayConfig.addressesSet[addr]; !ok {
			if sum.GatewayConfig.addressesSet == nil {
				sum.GatewayConfig.addressesSet = make(map[string]struct{})
			}
			sum.GatewayConfig.addressesSet[addr] = struct{}{}
			sum.GatewayConfig.Addresses = append(
				sum.GatewayConfig.Addresses, addr,
			)
		}
	}
}