package main

import (
	"context"
	"flag"
	"fmt"
	"io"
	"sort"
	"strings"
	"time"

	"felis.lolicon.best/internal/updater"
	"felis.lolicon.best/internal/updates"
)

// updateTimeout bounds the whole discovery pass. Each release source already caps
// its own HTTP client, but a hung DNS or a stalled TLS handshake would otherwise
// leave the operator staring at a silent terminal.
const updateTimeout = 60 * time.Second

// updateTarget maps a user-facing selector (`--panel`) onto the planner's component
// name and the command that actually performs the update.
//
// The apply side is deliberately NOT implemented in this command. Every component
// here is installed by deploy/bootstrap.sh, which is idempotent, already handles the
// parts that are easy to get wrong (Velocity's pinned MINOR, the atomic jar install,
// the image re-import + registry push that a byte-identical StatefulSet template
// will not trigger on its own), and is the path that gets exercised on every
// install. A
// second installer living in this file would duplicate that policy, could drift from
// it silently, and would be reachable only on a live node where a mistake takes the
// proxy or the control plane down. So `felis update` reports, and hands the operator
// the tested command — it does not re-implement it.
type updateTarget struct {
	// selector is the flag name without dashes.
	selector string
	// component is the updates planner's name for this piece, or "" when the planner
	// deliberately does not track it (Minecraft, which is pinned).
	component string
	// note explains what this selector covers, printed above the command.
	note string
	// command is the exact, already-tested way to apply it.
	command string
}

// installerRerun is the tested apply path for every planner-backed selector: re-run the
// installer. It is idempotent, and it is the only path that fetches a newer version --
// `felis setup` skips its host-bootstrap phase on a completed install (all four install
// markers already exist), so there it opens the config console and moves no component,
// and even on the bootstrap path it re-images felis-api from the binary setup is already
// running (FELIS_BOOTSTRAP_BINARY), which looks like an update and changes nothing.
//
// The URL is the same one-liner both READMEs hand out. While the repo is private it
// answers 404 (raw.githubusercontent.com hides private repos), which is why the trailer
// below points at the README's token'd form for that case.
const installerRerun = "curl -fsSL https://raw.githubusercontent.com/FelisMC/Felis/main/deploy/bootstrap.sh | sudo bash"

// updateTargets is the selector table. panel and plugins both resolve to felis-api
// because they are not separately versioned: the panel is compiled into the felis
// binary with //go:embed, and the plugin jars are built from this same repo in the
// same bootstrap run, so all three move together and carry one version.
var updateTargets = []updateTarget{
	{
		selector:  "panel",
		component: "felis-api",
		note:      "the panel is embedded in the felis binary (//go:embed), so updating it means rebuilding the felis image and rolling felis-api",
		command:   installerRerun,
	},
	{
		selector:  "velocity",
		component: "velocity",
		note:      "re-runs install_velocity: newest BUILD of the pinned minor (FELIS_VELOCITY_VERSION), atomic jar install, then restarts felis-velocity",
		command:   installerRerun,
	},
	{
		selector:  "plugins",
		component: "felis-api",
		note:      "felis-velocity.jar is a host-file swap, but felis-paper.jar and felis-limbo.jar are baked into the lobby/limbo images and need a rebuild + re-mirror into the in-cluster registry (the installer re-run does both)",
		command:   installerRerun,
	},
	{
		selector:  "mc",
		component: "", // never tracked: see the pin note below
		note:      "Minecraft is pinned by policy (\"能不动的就别动\") and Felis never proposes a version change for it. A server's version is a property of that server's image — change it on the server, not through a platform update",
		command:   "",
	},
}

// cmdUpdate reports what can be updated and what is already current.
//
// Bare `felis update` prints the status of every tracked component. Selector flags
// (--panel/--velocity/--mc/--plugins/--all) narrow that report to the components
// they name AND print how to apply each one. --force additionally prints the apply
// instruction for a selected component that is already up to date, for the
// reinstall/repair case.
//
// It never applies anything and never mutates the node, so unlike setup/breakGlass
// it needs no root. The versions it reads come from this host: k3s and cloudflared
// answer `--version`, Velocity's version is read out of the installed jar's
// manifest, and felis-api's is this binary's own build stamp — the same value
// `felis version` prints, which is what the user asked to be the source of truth.
func cmdUpdate(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("update", flag.ContinueOnError)
	fs.SetOutput(stderr)
	panel := fs.Bool("panel", false, "select the panel + control plane (felis-api)")
	velocity := fs.Bool("velocity", false, "select the Velocity proxy")
	mc := fs.Bool("mc", false, "select Minecraft (pinned; reported only)")
	plugins := fs.Bool("plugins", false, "select the Felis plugin jars (velocity/paper/limbo)")
	all := fs.Bool("all", false, "select every component above")
	force := fs.Bool("force", false, "print the apply command for a selected component even when it is already up to date")
	velocityJar := fs.String("velocity-jar", updater.DefaultVelocityJarPath, "path to the installed Velocity jar to read the current version from")
	if err := fs.Parse(args); err != nil {
		return 2
	}
	if fs.NArg() > 0 {
		fmt.Fprintf(stderr, "felis update: unexpected argument %q (this command takes flags only)\n", fs.Arg(0))
		return 2
	}

	selected := map[string]bool{}
	for sel, on := range map[string]bool{"panel": *panel, "velocity": *velocity, "mc": *mc, "plugins": *plugins} {
		if on || *all {
			selected[sel] = true
		}
	}

	ctx, cancel := context.WithTimeout(context.Background(), updateTimeout)
	defer cancel()

	rn := &updater.Runner{
		Gatherer: updater.NewHostGatherer(resolvedVersion(), *velocityJar),
		Source:   updater.NewRoutingSource(updater.Topology()),
		// Notifier and Applier stay nil on purpose: a human typing this command IS the
		// notification, and nothing here applies. The zero Window below means every
		// Scheduled component degrades to a notify, so the report can never claim an
		// apply is under way.
	}
	res, err := rn.Run(ctx, time.Now(), updates.Window{})
	if err != nil {
		fmt.Fprintf(stderr, "felis update: %v\n", err)
		return 1
	}

	fmt.Fprint(stdout, renderUpdateReport(res, selected))
	if len(selected) > 0 {
		fmt.Fprint(stdout, renderApplyGuidance(res, selected, *force))
	}
	return 0
}

// renderUpdateReport renders the component status table. With no selectors it shows
// every tracked component; with selectors it shows only the components those
// selectors name, so `felis update --velocity` is a focused answer rather than the
// whole platform. Components whose current version could not be read are listed
// separately rather than silently dropped — a component missing from the table with
// no explanation reads as "fine", which is the one thing it is not.
func renderUpdateReport(res updater.Result, selected map[string]bool) string {
	plan := res.RunResult.Plan
	if len(selected) > 0 {
		want := map[string]bool{}
		for _, t := range updateTargets {
			if selected[t.selector] && t.component != "" {
				want[t.component] = true
			}
		}
		filtered := make([]updates.Action, 0, len(plan))
		for _, a := range plan {
			if want[a.Component] {
				filtered = append(filtered, a)
			}
		}
		plan = filtered
	}

	var b strings.Builder
	if len(plan) > 0 {
		b.WriteString(updates.Report(plan))
	}

	// Two different failures both end up as a component the report cannot speak to,
	// and both are printed rather than swallowed. A component that simply vanishes
	// from the table reads as "fine", and a bare "latest unknown" line reads as "there
	// is nothing newer" — when the truth may be that the release feed was unreachable.
	// Naming the cause is the difference between a report and a guess.
	writeErrs(&b, "current version unreadable", res.GatherErrors, selected)
	writeErrs(&b, "latest version undiscoverable", res.RunResult.SourceErrors, selected)

	// With selectors active an empty table is not a surprise — `--mc` names a component
	// the planner deliberately does not track — and the guidance below already explains
	// it, so stay quiet rather than printing a bare "nothing matched" that reads as an
	// error. Without selectors an empty table means nothing is tracked at all, which
	// does need saying.
	if b.Len() == 0 && len(selected) == 0 {
		return "No components tracked.\n"
	}
	return b.String()
}

// writeErrs appends one explanatory line per failed component, in a stable order so
// the output does not shuffle between runs, honouring the active selector filter.
func writeErrs(b *strings.Builder, label string, errs map[string]error, selected map[string]bool) {
	names := make([]string, 0, len(errs))
	for name := range errs {
		names = append(names, name)
	}
	sort.Strings(names)
	for _, name := range names {
		if len(selected) > 0 && !selectedCovers(selected, name) {
			continue
		}
		fmt.Fprintf(b, "%-13s %s: %v\n", name, label, errs[name])
	}
}

// selectedCovers reports whether any chosen selector maps to this component.
func selectedCovers(selected map[string]bool, component string) bool {
	for _, t := range updateTargets {
		if selected[t.selector] && t.component == component {
			return true
		}
	}
	return false
}

// renderApplyGuidance prints, for each selected target, how to actually apply the
// update. A target that is already current is skipped unless --force was passed.
func renderApplyGuidance(res updater.Result, selected map[string]bool, force bool) string {
	byComponent := map[string]updates.Action{}
	for _, a := range res.RunResult.Plan {
		byComponent[a.Component] = a
	}

	var b strings.Builder
	var offeredCommand bool
	for _, t := range updateTargets {
		if !selected[t.selector] {
			continue
		}
		// Minecraft has no planner entry by design; state the pin and move on. There is
		// no command to offer, so this must not arm the trailer below.
		if t.component == "" {
			fmt.Fprintf(&b, "\n--%s: %s.\n", t.selector, t.note)
			continue
		}
		a, planned := byComponent[t.component]
		// "Up to date" requires actually KNOWING the latest version. ActionNone covers
		// both "nothing newer exists" and "the release feed could not be read", and
		// collapsing those would report an unreachable upstream as currency — telling an
		// operator they are current when nobody checked is the one answer an update tool
		// must never give. LatestKnown is what separates them.
		if planned && a.Kind == updates.ActionNone && a.LatestKnown && !force {
			fmt.Fprintf(&b, "\n--%s: %s is already up to date; nothing to apply (use --force to reinstall anyway).\n", t.selector, t.component)
			continue
		}
		fmt.Fprintf(&b, "\n--%s: %s\n", t.selector, t.note)
		if planned && !a.LatestKnown {
			// Unknown latest still offers the command: the operator asked about this
			// component, and reinstalling the current release is a valid repair action.
			fmt.Fprintf(&b, "  note: cannot tell whether %s is current — its latest version could not be discovered (see above); this reinstalls it either way\n", t.component)
		}
		fmt.Fprintf(&b, "  run: %s\n", t.command)
		offeredCommand = true
	}
	// Only explain the command when one was actually offered; a --mc-only run has
	// nothing to run and the trailer would be a non-sequitur.
	//
	// One trailer serves every selector now: setup is not an apply path at all on a
	// completed install (shouldRunHostBootstrapBeforeConfig only enters the host
	// bootstrap while an install marker is missing), so the installer re-run is the one
	// worked path for all three components and there is no per-component exception left
	// to scope. Two caveats stay because following the advice without them bites real
	// hosts: the channel is not persisted anywhere (a bare re-run on a main host quietly
	// moves it onto releases), and the private repo's one-liner needs the read token
	// back in the environment before it can resolve anything.
	if offeredCommand {
		b.WriteString("\nRe-running the installer applies everything above: it fetches the newest version on\nthe channel in effect and re-applies the bundle (release is the default). The channel\nis not persisted, so pass FELIS_VERSION_BOOTSTRAP=dev if this host tracks main. While\nthis repo is private, the one-liner above 404s without a token; the README's install\nsection has the token'd form that works. felis setup is not this path: on a completed\ninstall it opens the config console and installs nothing newer. Restart game servers\nafterwards.\n")
	}
	return b.String()
}