// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>

package main

import (
	"context"
	"fmt"
	"os"
	"strings"
	"text/tabwriter"
	"time"

	"git.ipng.ch/ipng/vpp-maglev/internal/grpcapi"
)

const callTimeout = 10 * time.Second

// buildTree constructs the full command tree.
func buildTree() *Node {
	root := &Node{Word: "", Help: ""}

	show := &Node{Word: "show", Help: "show information"}
	set := &Node{Word: "set", Help: "modify configuration"}
	quit := &Node{Word: "quit", Help: "exit the shell", Run: runQuit}
	exit := &Node{Word: "exit", Help: "exit the shell", Run: runQuit}

	// show frontends
	showFrontends := &Node{Word: "frontends", Help: "list all frontends", Run: runShowFrontends}
	// show frontend <name>
	showFrontendName := &Node{
		Word:    "<name>",
		Help:    "frontend name",
		Dynamic: dynFrontends,
		Run:     runShowFrontend,
	}
	showFrontend := &Node{
		Word:     "frontend",
		Help:     "show a single frontend",
		Children: []*Node{showFrontendName},
	}

	// show backends
	showBackends := &Node{Word: "backends", Help: "list all backends", Run: runShowBackends}
	// show backend <name>
	showBackendName := &Node{
		Word:    "<name>",
		Help:    "backend name",
		Dynamic: dynBackends,
		Run:     runShowBackend,
	}
	showBackend := &Node{
		Word:     "backend",
		Help:     "show a single backend",
		Children: []*Node{showBackendName},
	}

	// show healthchecks
	showHealthChecks := &Node{Word: "healthchecks", Help: "list all health checks", Run: runShowHealthChecks}
	// show healthcheck <name>
	showHealthCheckName := &Node{
		Word:    "<name>",
		Help:    "health check name",
		Dynamic: dynHealthChecks,
		Run:     runShowHealthCheck,
	}
	showHealthCheck := &Node{
		Word:     "healthcheck",
		Help:     "show a single health check",
		Children: []*Node{showHealthCheckName},
	}

	show.Children = []*Node{
		showFrontends, showFrontend,
		showBackends, showBackend,
		showHealthChecks, showHealthCheck,
	}

	// set backend <name> pause|resume|disabled|enabled
	setPause := &Node{Word: "pause", Help: "pause health checking", Run: runPauseBackend}
	setResume := &Node{Word: "resume", Help: "resume health checking", Run: runResumeBackend}
	setDisabled := &Node{Word: "disabled", Help: "disable backend (not implemented)", Run: runNotImplemented}
	setEnabled := &Node{Word: "enabled", Help: "enable backend (not implemented)", Run: runNotImplemented}
	setBackendName := &Node{
		Word:    "<name>",
		Help:    "backend name",
		Dynamic: dynBackends,
		Children: []*Node{setPause, setResume, setDisabled, setEnabled},
	}
	setBackend := &Node{
		Word:     "backend",
		Help:     "modify a backend",
		Children: []*Node{setBackendName},
	}
	set.Children = []*Node{setBackend}

	root.Children = []*Node{show, set, quit, exit}
	return root
}

// ---- dynamic enumerators ---------------------------------------------------

func dynFrontends(ctx context.Context, client grpcapi.MaglevClient) []string {
	resp, err := client.ListFrontends(ctx, &grpcapi.ListFrontendsRequest{})
	if err != nil {
		return nil
	}
	return resp.FrontendNames
}

func dynBackends(ctx context.Context, client grpcapi.MaglevClient) []string {
	resp, err := client.ListBackends(ctx, &grpcapi.ListBackendsRequest{})
	if err != nil {
		return nil
	}
	return resp.BackendNames
}

func dynHealthChecks(ctx context.Context, client grpcapi.MaglevClient) []string {
	resp, err := client.ListHealthChecks(ctx, &grpcapi.ListHealthChecksRequest{})
	if err != nil {
		return nil
	}
	return resp.Names
}

// ---- run functions ---------------------------------------------------------

func runQuit(_ context.Context, _ grpcapi.MaglevClient, _ []string) error {
	return errQuit
}

func runShowFrontends(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	resp, err := client.ListFrontends(ctx, &grpcapi.ListFrontendsRequest{})
	if err != nil {
		return err
	}
	for _, name := range resp.FrontendNames {
		fmt.Println(name)
	}
	return nil
}

func runShowFrontend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: show frontend <name>")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.GetFrontend(ctx, &grpcapi.GetFrontendRequest{Name: args[0]})
	if err != nil {
		return err
	}
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "name\t%s\n", info.Name)
	fmt.Fprintf(w, "address\t%s\n", info.Address)
	fmt.Fprintf(w, "protocol\t%s\n", info.Protocol)
	fmt.Fprintf(w, "port\t%d\n", info.Port)
	for i, b := range info.BackendNames {
		if i == 0 {
			fmt.Fprintf(w, "backends\t%s\n", b)
		} else {
			fmt.Fprintf(w, "\t%s\n", b)
		}
	}
	if info.Description != "" {
		fmt.Fprintf(w, "description\t%s\n", info.Description)
	}
	return w.Flush()
}

func runShowBackends(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	resp, err := client.ListBackends(ctx, &grpcapi.ListBackendsRequest{})
	if err != nil {
		return err
	}
	for _, name := range resp.BackendNames {
		fmt.Println(name)
	}
	return nil
}

func runShowBackend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: show backend <name>")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.GetBackend(ctx, &grpcapi.GetBackendRequest{Name: args[0]})
	if err != nil {
		return err
	}
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "name\t%s\n", info.Name)
	fmt.Fprintf(w, "address\t%s\n", info.Address)
	stateDur := ""
	if len(info.Transitions) > 0 {
		since := time.Since(time.Unix(0, info.Transitions[0].AtUnixNs))
		stateDur = " for " + formatDuration(since)
	}
	fmt.Fprintf(w, "state\t%s%s\n", info.State, stateDur)
	fmt.Fprintf(w, "enabled\t%v\n", info.Enabled)
	fmt.Fprintf(w, "weight\t%d\n", info.Weight)
	fmt.Fprintf(w, "healthcheck\t%s\n", info.Healthcheck)
	for i, t := range info.Transitions {
		ts := time.Unix(0, t.AtUnixNs)
		label := ""
		if i == 0 {
			label = "transitions"
		}
		fmt.Fprintf(w, "%s\t%s → %s\t%s\t%s\n",
			label,
			t.From, t.To,
			ts.Format("2006-01-02 15:04:05.000"),
			formatAgo(time.Since(ts)),
		)
	}
	return w.Flush()
}

func runShowHealthChecks(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	resp, err := client.ListHealthChecks(ctx, &grpcapi.ListHealthChecksRequest{})
	if err != nil {
		return err
	}
	for _, name := range resp.Names {
		fmt.Println(name)
	}
	return nil
}

func runShowHealthCheck(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: show healthcheck <name>")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.GetHealthCheck(ctx, &grpcapi.GetHealthCheckRequest{Name: args[0]})
	if err != nil {
		return err
	}
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "name\t%s\n", info.Name)
	fmt.Fprintf(w, "type\t%s\n", info.Type)
	if info.Port > 0 {
		fmt.Fprintf(w, "port\t%d\n", info.Port)
	}
	fmt.Fprintf(w, "interval\t%s\n", time.Duration(info.IntervalNs))
	if info.FastIntervalNs > 0 {
		fmt.Fprintf(w, "fast-interval\t%s\n", time.Duration(info.FastIntervalNs))
	}
	if info.DownIntervalNs > 0 {
		fmt.Fprintf(w, "down-interval\t%s\n", time.Duration(info.DownIntervalNs))
	}
	fmt.Fprintf(w, "timeout\t%s\n", time.Duration(info.TimeoutNs))
	fmt.Fprintf(w, "rise\t%d\n", info.Rise)
	fmt.Fprintf(w, "fall\t%d\n", info.Fall)
	if info.ProbeIpv4Src != "" {
		fmt.Fprintf(w, "probe-ipv4-src\t%s\n", info.ProbeIpv4Src)
	}
	if info.ProbeIpv6Src != "" {
		fmt.Fprintf(w, "probe-ipv6-src\t%s\n", info.ProbeIpv6Src)
	}
	if h := info.Http; h != nil {
		fmt.Fprintf(w, "http.path\t%s\n", h.Path)
		if h.Host != "" {
			fmt.Fprintf(w, "http.host\t%s\n", h.Host)
		}
		fmt.Fprintf(w, "http.response-code\t%d-%d\n", h.ResponseCodeMin, h.ResponseCodeMax)
		if h.ResponseRegexp != "" {
			fmt.Fprintf(w, "http.response-regexp\t%s\n", h.ResponseRegexp)
		}
	}
	if t := info.Tcp; t != nil {
		fmt.Fprintf(w, "tcp.ssl\t%v\n", t.Ssl)
		if t.ServerName != "" {
			fmt.Fprintf(w, "tcp.server-name\t%s\n", t.ServerName)
		}
	}
	return w.Flush()
}

func runPauseBackend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: set backend <name> pause")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.PauseBackend(ctx, &grpcapi.PauseResumeRequest{Name: args[0]})
	if err != nil {
		return err
	}
	fmt.Printf("%s: setting state to '%s'\n", info.Name, info.State)
	return nil
}

func runResumeBackend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: set backend <name> resume")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.ResumeBackend(ctx, &grpcapi.PauseResumeRequest{Name: args[0]})
	if err != nil {
		return err
	}
	fmt.Printf("%s: setting state to '%s'\n", info.Name, info.State)
	return nil
}

func runNotImplemented(_ context.Context, _ grpcapi.MaglevClient, _ []string) error {
	fmt.Println("not implemented yet")
	return nil
}

// formatDuration formats a duration as Xd Xh Xm Xs without milliseconds.
func formatDuration(d time.Duration) string {
	if d < 0 {
		d = 0
	}
	d = d.Truncate(time.Second)

	days := int(d.Hours()) / 24
	d -= time.Duration(days) * 24 * time.Hour
	hours := int(d.Hours())
	d -= time.Duration(hours) * time.Hour
	minutes := int(d.Minutes())
	d -= time.Duration(minutes) * time.Minute
	seconds := int(d.Seconds())

	var b strings.Builder
	if days > 0 {
		fmt.Fprintf(&b, "%dd", days)
	}
	if hours > 0 {
		fmt.Fprintf(&b, "%dh", hours)
	}
	if minutes > 0 {
		fmt.Fprintf(&b, "%dm", minutes)
	}
	if seconds > 0 || b.Len() == 0 {
		fmt.Fprintf(&b, "%ds", seconds)
	}
	return b.String()
}

func formatAgo(d time.Duration) string {
	return formatDuration(d) + " ago"
}