package main

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"strings"
	"time"

	"github.com/novox/mesh-control/internal/broker"
	"github.com/novox/mesh-control/internal/inventory"
	"github.com/novox/mesh-control/internal/link"
	"github.com/novox/mesh-control/internal/token"
)

// what a machine is, and what it is allowed to be told.
//
// Split out of main.go, which had reached 2,769 lines because appending was always the
// cheapest next step. That is how novox/hq ADR 0001 records `hal/sdk` reaching 34,636:
// nothing in it was wrong, and no one edit was the one that should have been a new file.

func nodeCommand(ctx context.Context, args []string) error {
	if len(args) == 0 {
		return errors.New("node add <name>, node list, node show <name>, or " + publicDomainUsage)
	}
	open, err := openStores(ctx)
	if err != nil {
		return err
	}
	defer open.Close()
	inv := open.inventory

	switch args[0] {
	case "show":
		if len(args) != 2 {
			return errors.New("node show <name>")
		}
		return showNode(ctx, inv, args[1])
	case "add":
		if len(args) != 2 {
			return errors.New("node add <name>")
		}
		node, err := inv.AddNode(ctx, args[1])
		if err != nil {
			return err
		}
		fmt.Printf("added %s (%s)\n", node.Name, node.ID)
		return nil

	case "list":
		nodes, err := inv.Nodes(ctx)
		if err != nil {
			return err
		}
		if len(nodes) == 0 {
			// Said rather than printed as nothing: an empty list and a failed read must never
			// look the same, and this command answering "none" is only honest because getting
			// here means the store answered.
			fmt.Println("this mesh has no node records yet")
			return nil
		}
		for _, n := range nodes {
			fmt.Printf("%-20s %-14s %s\n", n.Name, heardFrom(n), n.ID)
		}
		return nil

	case "public-domain":
		// The domain this node composes its routed names under (novox/hq ADR 0066).
		//
		// **The form with no argument reports; clearing is asked for by name.** It used to clear —
		// so `node public-domain anchor`, which reads like a question and is what anybody types to
		// find out what the answer is, silently took every routed name the node had. A read-shaped
		// invocation must never be a destructive write: there is no output that makes up for it,
		// because the damage is already done by the time it prints.
		return publicDomain(ctx, inv, args[1:])

	default:
		return fmt.Errorf("node has no %q; it has add, list, show and public-domain", args[0])
	}
}

// publicDomainUsage is the one description of the three forms, so a refusal and the help agree.
const publicDomainUsage = "node public-domain <name> — what it is now; " +
	"<name> <domain> to set it; <name> --clear to take it away"

// publicDomain reads, sets or clears the domain a node composes its routed names under.
//
// Three forms, and the destructive one is the only one that has to be asked for. Clearing is a
// real thing to want — a machine that stops facing the outside composes no names, and
// lab-versus-production is this one setting (novox/hq ADR 0066) — so it keeps a way to say it.
// What it does not keep is being the thing that happens when nothing was said at all.
func publicDomain(ctx context.Context, inv *inventory.Inventory, args []string) error {
	set := flag.NewFlagSet("node public-domain", flag.ContinueOnError)
	clear := set.Bool("clear", false, "take the domain away; it composes no routed names after")
	positionals, err := parseAround(set, args)
	if err != nil {
		return err
	}
	if len(positionals) == 0 || len(positionals) > 2 {
		return errors.New(publicDomainUsage)
	}
	node := positionals[0]

	switch {
	case *clear && len(positionals) == 2:
		// Both, which cannot be meant. Refused rather than one of them silently winning.
		return fmt.Errorf("give %s a domain or --clear, not both: %q and --clear say opposite "+
			"things and the mesh will not choose between them", node, positionals[1])

	case *clear:
		if err := inv.SetPublicDomain(ctx, node, ""); err != nil {
			return err
		}
		fmt.Printf("%s has no public domain, so it composes no routed names\n", node)
		fmt.Printf("  run `push %s` to take them off it\n", node)
		return nil

	case len(positionals) == 2:
		if err := inv.SetPublicDomain(ctx, node, positionals[1]); err != nil {
			return err
		}
		fmt.Printf("%s composes its routed names under %s\n", node, positionals[1])
		fmt.Printf("  run `push %s` to send it\n", node)
		return nil

	default:
		// Asked, so answered. NodeByName first, so a name the mesh has never heard of is a refusal
		// rather than "it has no public domain", which is true of that name and says nothing.
		if _, err := inv.NodeByName(ctx, node); err != nil {
			return err
		}
		domain, err := inv.PublicDomainOf(ctx, node)
		if err != nil {
			return err
		}
		if domain == "" {
			fmt.Printf("%s has no public domain, so it composes no routed names\n", node)
			fmt.Printf("  `node public-domain %s <domain>` gives it one\n", node)
			return nil
		}
		fmt.Printf("%s composes its routed names under %s\n", node, domain)
		return nil
	}
}

func tokenCommand(ctx context.Context, args []string) error {
	if len(args) == 0 || args[0] != "issue" {
		return errors.New("token issue --node <name>, or token issue --new <name>")
	}

	set := flag.NewFlagSet("token issue", flag.ContinueOnError)
	existing := set.String("node", "", "issue for a node record that already exists")
	fresh := set.String("new", "", "create the node record, then issue for it")
	validFor := set.Duration("for", time.Hour, "how long the token may be used")
	if err := set.Parse(args[1:]); err != nil {
		return err
	}

	// Exactly one, because the difference is what the token binds to. A command that guessed
	// would sometimes create a second record for a machine that already has one.
	if (*existing == "") == (*fresh == "") {
		return errors.New("give exactly one of --node <name> or --new <name>: the first is a " +
			"machine the mesh already has a record for, the second is one it has never seen")
	}

	open, err := openStores(ctx)
	if err != nil {
		return err
	}
	defer open.Close()
	inv := open.inventory

	name := *existing
	if *fresh != "" {
		node, err := inv.AddNode(ctx, *fresh)
		if err != nil {
			return err
		}
		name = node.Name
	}

	issued, err := inv.IssueToken(ctx, name, *validFor)
	if err != nil {
		return err
	}

	// Assembled from two contexts by the process that holds both grants. Neither reads the
	// other's store (novox/hq ADR 0008) — each is asked for its own part.
	ident, err := openIdentity(ctx)
	if err != nil {
		return err
	}
	defer ident.Close()
	key, err := ident.Establish(ctx)
	if err != nil {
		return err
	}

	// The account is created before the token is handed over, which is what removes the
	// chicken-and-egg entirely: the mesh runs the broker, so a joining node's credentials can
	// exist before it does. The one-time secret IS the password, so a node's first connection is
	// already authenticated and enrolment is what happens over it.
	if management, err := broker.ManagementFromEnvironment(); err == nil {
		if err := management.CreateNodeAccount(ctx, issued.Node.Name, issued.Secret); err != nil {
			return err
		}
		fmt.Printf("broker account %s created, scoped to %s and the %s exchange\n\n",
			issued.Node.Name, link.QueueFor(issued.Node.Name), link.Exchange)
	} else if !errors.Is(err, broker.ErrNotConfigured) {
		return err
	}

	made := token.Token{Node: issued.Node.Name, Signer: key.Public, Secret: issued.Secret}

	// Absent is a state, not a failure: a control plane can hold records and a key before it has
	// a broker. What it cannot do is issue a token anybody could use, and Missing() says so.
	known, err := broker.FromEnvironment()
	switch {
	case err == nil:
		made.Broker, made.Fingerprint = known.Address, known.Fingerprint
	case errors.Is(err, broker.ErrNotConfigured):
	default:
		return err
	}
	encoded, err := made.Encode()
	if err != nil {
		return err
	}

	fmt.Printf("token for %s, usable once, until %s\n\n  %s\n\n",
		issued.Node.Name, issued.Expires.Format(time.RFC3339), encoded)
	fmt.Println("This is the only time it is shown. What is stored is a hash of the secret.")

	if missing := made.Missing(); len(missing) > 0 {
		fmt.Printf("\nINCOMPLETE — this token cannot be used to join anything yet. Missing:\n")
		for _, m := range missing {
			fmt.Printf("  - %s\n", m)
		}
		fmt.Printf("\nSet %s and %s once the broker is raised.\n",
			broker.AddressVar, broker.CertificateVar)
	}
	return nil
}

func identityCommand(ctx context.Context, args []string) error {
	if len(args) == 0 || args[0] != "show" {
		return errors.New("identity show")
	}
	ident, err := openIdentity(ctx)
	if err != nil {
		return err
	}
	defer ident.Close()

	// Establish rather than read: a control plane asked for its identity before it has one should
	// get one, not an error. Generating it is idempotent, so this is safe to run at any time.
	key, err := ident.Establish(ctx)
	if err != nil {
		return err
	}
	fmt.Printf("signing key   %s\n", key.ID)
	fmt.Printf("fingerprint   %s\n", key.Fingerprint())
	fmt.Printf("created       %s\n", key.Created.Format(time.RFC3339))
	fmt.Printf("\nThe public half of this travels in every enrolment token. A node believes a\n" +
		"declaration because it carries a signature this key made (novox/hq ADR 0004).\n")
	return nil
}

func brokerCommand(args []string) error {
	if len(args) == 0 || args[0] != "show" {
		return errors.New("broker show")
	}
	known, err := broker.FromEnvironment()
	if errors.Is(err, broker.ErrNotConfigured) {
		fmt.Printf("no broker configured. Set %s and %s.\n\n"+
			"Until then tokens carry the signing key and the one-time secret, and say what they\n"+
			"are missing. They cannot be used to join.\n",
			broker.AddressVar, broker.CertificateVar)
		return nil
	}
	if err != nil {
		return err
	}
	fmt.Printf("address       %s\n", known.Address)
	fmt.Printf("fingerprint   %s\n", known.Fingerprint)
	fmt.Print("\nThe fingerprint is computed from the certificate on disk, never configured. A\n" +
		"node checks it before sending anything (novox/hq ADR 0004).\n")
	return nil
}

// heardFrom says when a node was last heard from, in a form somebody can act on.
//
// "never" and "an hour ago" are different answers and are kept different. A node that has never
// spoken did not finish joining; a node last heard from an hour ago is running an hour-old
// picture of the mesh.
func heardFrom(n inventory.Node) string {
	silent, ever := n.Silent()
	switch {
	case !ever:
		return "never spoken"
	case silent > SilentFor:
		return "out of touch " + roughly(silent)
	default:
		return "here"
	}
}

// roughly is a duration a person reads rather than parses.
func roughly(d time.Duration) string {
	switch {
	case d < time.Hour:
		return fmt.Sprintf("%dm", int(d.Minutes()))
	case d < 48*time.Hour:
		return fmt.Sprintf("%dh", int(d.Hours()))
	default:
		return fmt.Sprintf("%dd", int(d.Hours()/24))
	}
}

// showNode says what one machine reported about itself, in its own words.
//
// **A capability is detected and never assumed** (novox/hq ADR 0009), so the only account of what
// a machine can do is the one it gave — and its detail is half of that account. The mesh was
// keeping the yes and discarding the reason, which makes *this machine has no seat* an answer with
// nowhere to go: a person told a machine lacks something wants to know what the detector saw.
//
// It is also where "what should it be configured as" is read. The same line that gates an
// assignment carries `card1-DP-1`, and a person composing settings for that machine needs it.
func showNode(ctx context.Context, inv *inventory.Inventory, name string) error {
	node, err := inv.NodeByName(ctx, name)
	if err != nil {
		return err
	}
	fmt.Printf("%s\n", node.Name)
	fmt.Printf("  last heard from   %s\n", heardFrom(node))

	// The domain its routed names are composed under, when it has one (novox/hq ADR 0066). Shown
	// only when set: a machine that serves nothing to the outside has no domain, and saying so of
	// every internal node would be noise.
	domain, err := inv.PublicDomainOf(ctx, name)
	if err != nil {
		return err
	}
	if domain != "" {
		fmt.Printf("  public domain     %s\n", domain)
	}

	held, err := inv.Profile(ctx, name)
	if err != nil {
		return err
	}
	if held == nil {
		// Never reported is not the same as reported nothing, and the remedy differs: one is a
		// machine that has not run the host yet, the other is a machine that ran it and can do
		// nothing.
		fmt.Printf("\n  this machine has never said what it can do, so everything requiring a\n" +
			"  capability is refused here — run the host on it\n")
		return nil
	}
	if len(held) == 0 {
		fmt.Printf("\n  it reported no capabilities at all\n")
		return nil
	}

	fmt.Printf("\n  what it can do, as it reported:\n")
	for _, c := range held {
		mark := "no "
		if c.Present {
			mark = "yes"
		}
		fmt.Printf("    %s  %-20s %s\n", mark, c.Name, c.Detail)
	}

	assigned, err := inv.Assigned(ctx, name)
	if err != nil {
		return err
	}
	if len(assigned) > 0 {
		fmt.Printf("\n  assigned: %s\n", strings.Join(assigned, ", "))
	}
	return nil
}