package main

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"os"
	"strings"

	agentpb "git.ipao.vip/rogee/go-sip/gen/agent"
	"git.ipao.vip/rogee/go-sip/internal/config"
	"git.ipao.vip/rogee/go-sip/internal/rpc"
	"github.com/spf13/cobra"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
)

func newCurrentAgentCommand() *cobra.Command {
	var mode string
	command := &cobra.Command{
		Use: "agent", Short: "Run the isolated Agent", Args: cobra.NoArgs,
		SilenceUsage: true,
		RunE: func(cmd *cobra.Command, _ []string) error {
			settings, err := config.LoadAgentEnvironment(mode)
			if err != nil {
				return err
			}
			scenario, err := loadApprovedMockScenario(settings.MockScenarioFile)
			if err != nil {
				return err
			}
			applied, err := loadMockAppliedSIP(settings.MockAppliedSIPFile)
			if err != nil {
				return err
			}
			ca, err := readAgentPEM("MTLS_CA_FILE", settings.CAFile)
			if err != nil {
				return err
			}
			cert, err := readAgentPEM("MTLS_CERT_FILE", settings.CertFile)
			if err != nil {
				return err
			}
			key, err := readAgentPEM("MTLS_KEY_FILE", settings.KeyFile)
			if err != nil {
				return err
			}
			serverTLS, err := rpc.NewServerTLSConfig(ca, cert, key)
			if err != nil {
				return errors.New("Agent mTLS listener certificate is invalid")
			}
			clientTLS, err := rpc.NewClientTLSConfig(ca, cert, key, settings.DispatcherServerName)
			if err != nil {
				return errors.New("Agent mTLS Dispatcher certificate configuration is invalid")
			}
			connection, err := grpc.NewClient(settings.DispatcherEndpoint, grpc.WithTransportCredentials(credentials.NewTLS(clientTLS)))
			if err != nil {
				return errors.New("Agent cannot create pinned Dispatcher connection")
			}
			defer connection.Close()
			handler, err := newCurrentAgentServer(cmd.Context(), settings, scenario, applied, agentpb.NewAgentControlServiceClient(connection))
			if err != nil {
				return err
			}
			listener, err := net.Listen("tcp", settings.Listen)
			if err != nil {
				return fmt.Errorf("Agent cannot listen on configured Mock address: %w", err)
			}
			defer listener.Close()
			server := grpc.NewServer(grpc.Creds(credentials.NewTLS(serverTLS)))
			agentpb.RegisterAgentControlServiceServer(server, handler)
			stopped := make(chan struct{})
			go func() {
				select {
				case <-cmd.Context().Done():
					server.GracefulStop()
				case <-stopped:
				}
			}()
			err = server.Serve(listener)
			close(stopped)
			if err != nil && !errors.Is(err, grpc.ErrServerStopped) {
				return fmt.Errorf("Agent gRPC listener stopped: %w", err)
			}
			if cmd.Context().Err() == nil {
				return errors.New("Agent gRPC listener stopped without shutdown")
			}
			return nil
		},
	}
	command.Flags().StringVar(&mode, "mode", "mock", "isolated Mock mode only")
	return command
}

// This is an isolated deployment fixture, not SaaS SIP configuration or proof
// that Asterisk actually loaded the revisions. Real/mixed startup is rejected.
func loadMockAppliedSIP(path string) (map[string]int64, error) {
	if strings.TrimSpace(path) == "" {
		return nil, errors.New("AGENT_MOCK_APPLIED_SIP_FILE is required")
	}
	file, err := os.Open(path)
	if err != nil {
		return nil, errors.New("AGENT_MOCK_APPLIED_SIP_FILE cannot be opened")
	}
	defer file.Close()
	data, err := io.ReadAll(io.LimitReader(file, 64<<10+1))
	if err != nil || len(data) > 64<<10 {
		return nil, errors.New("AGENT_MOCK_APPLIED_SIP_FILE exceeds its size limit or cannot be read")
	}
	var fixture struct {
		Trunks map[string]int64 `json:"trunks"`
	}
	decoder := json.NewDecoder(bytes.NewReader(data))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&fixture); err != nil {
		return nil, errors.New("AGENT_MOCK_APPLIED_SIP_FILE has invalid fields")
	}
	if err := decoder.Decode(new(any)); err != io.EOF {
		return nil, errors.New("AGENT_MOCK_APPLIED_SIP_FILE contains extra data")
	}
	if len(fixture.Trunks) == 0 {
		return nil, errors.New("AGENT_MOCK_APPLIED_SIP_FILE requires explicit trunks")
	}
	for trunk, revision := range fixture.Trunks {
		if strings.TrimSpace(trunk) == "" || revision <= 0 {
			return nil, errors.New("AGENT_MOCK_APPLIED_SIP_FILE has invalid trunk revision")
		}
	}
	return fixture.Trunks, nil
}

func readAgentPEM(name, path string) ([]byte, error) {
	file, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("%s cannot be opened", name)
	}
	defer file.Close()
	data, err := io.ReadAll(io.LimitReader(file, 1<<20+1))
	if err != nil || len(data) == 0 || len(data) > 1<<20 {
		return nil, fmt.Errorf("%s is unreadable or too large", name)
	}
	return data, nil
}