package main

import (
	"bufio"
	"context"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"os"
	"strings"
)

// licenceCommand is everything about model access the mesh holds.
//
// **A licence is a named thing and the name is the operator's** (novox/hq ADR 0024). *The personal
// account*, *the organisation's account* — those are names a person uses, and the mesh has to use
// them too, because the whole point is saying which one a given consumer uses.
func licenceCommand(ctx context.Context, args []string) error {
	if len(args) == 0 {
		return errors.New("licence add|list|use|release|key|forget")
	}
	switch args[0] {
	case "add":
		return licenceAdd(ctx, args[1:])
	case "list":
		return licenceList(ctx)
	case "use":
		return licenceUse(ctx, args[1:], true)
	case "release":
		return licenceUse(ctx, args[1:], false)
	case "key":
		return licenceKey(ctx, args[1:])
	case "forget":
		return licenceForget(ctx, args[1:])
	}
	return fmt.Errorf("licence %q; it is add, list, use, release, key or forget", args[0])
}

func licenceAdd(ctx context.Context, args []string) error {
	set := flag.NewFlagSet("licence add", flag.ContinueOnError)
	// What a consumer must know that is not secret — a base URL, a model name. Never the key.
	serves := set.String("serves", "",
		"JSON a consumer must know that is not secret, such as a base URL or a model")
	positionals, err := parseAround(set, args)
	if err != nil {
		return err
	}
	if len(positionals) != 2 {
		return errors.New(`licence add <vendor> <name> [--serves '{"model":"..."}']`)
	}
	vendor, name := positionals[0], positionals[1]

	values := map[string]any{}
	if strings.TrimSpace(*serves) != "" {
		if err := json.Unmarshal([]byte(*serves), &values); err != nil {
			return fmt.Errorf("--serves is not JSON: %w", err)
		}
	}

	held, err := openLicences(ctx)
	if err != nil {
		return err
	}
	defer held.Close()
	if err := held.Add(ctx, name, vendor, values); err != nil {
		return err
	}
	fmt.Printf("%s (%s) recorded. Nothing uses it yet, and it has no key:\n"+
		"  licence use %s <node> <module>\n  licence key %s\n", name, vendor, name, name)
	return nil
}

func licenceList(ctx context.Context) error {
	held, err := openLicences(ctx)
	if err != nil {
		return err
	}
	defer held.Close()

	all, err := held.All(ctx)
	if err != nil {
		return err
	}
	if len(all) == 0 {
		// Said, not printed as nothing: an empty list and a failed read must never look the same.
		fmt.Println("this mesh holds no licences")
		return nil
	}
	for _, one := range all {
		holders, err := held.HoldersOf(ctx, one.Name)
		if err != nil {
			return err
		}
		fmt.Printf("%s  (%s)\n", one.Name, one.Vendor)
		if len(holders) == 0 {
			fmt.Printf("  nobody uses it\n")
		}
		for _, h := range holders {
			// Whether it has a key is the question somebody is actually asking, so it is said
			// per holder rather than per licence: the key was sealed to the holders that existed
			// when it was supplied, and one recorded afterwards has none.
			state := "has no key — supply it again with `licence key " + one.Name + "`"
			if h.Sealed != "" {
				state = "has a key"
			}
			fmt.Printf("  %s on %s: %s\n", h.Module, h.Node, state)
		}
	}
	return nil
}

func licenceUse(ctx context.Context, args []string, using bool) error {
	verb := "use"
	if !using {
		verb = "release"
	}
	if len(args) != 3 {
		return fmt.Errorf("licence %s <name> <node> <module>", verb)
	}
	name, node, module := args[0], args[1], args[2]

	held, err := openLicences(ctx)
	if err != nil {
		return err
	}
	defer held.Close()

	if !using {
		if err := held.StopUsing(ctx, name, node, module); err != nil {
			return err
		}
		fmt.Printf("%s on %s no longer uses %s. Its copy of the key goes on the next push\n",
			module, node, name)
		return nil
	}
	if err := held.Use(ctx, name, node, module); err != nil {
		return err
	}
	fmt.Printf("%s on %s uses %s.\n", module, node, name)
	// The consequence, said now rather than discovered as a machine that resolves and receives
	// nothing: the mesh discarded the plaintext, so a holder added after the key was supplied has
	// no key and the mesh cannot make one.
	sealed, err := held.KeyFor(ctx, name, node, module)
	if err != nil {
		return err
	}
	if sealed == "" {
		fmt.Printf("  It has no key yet — the mesh discarded the plaintext when it was supplied "+
			"and cannot seal another. Supply it again:\n  licence key %s\n", name)
	}
	return nil
}

// licenceKey is the *accept* verb novox/hq ADR 0024 names as missing.
//
// Take a value, seal it to each holder, and discard the plaintext. Every other credential the
// mesh handles it generated itself; an API key arrives from a person, and a mesh that kept
// operator-supplied keys readably is the arrangement this project measured and rejected.
func licenceKey(ctx context.Context, args []string) error {
	set := flag.NewFlagSet("licence key", flag.ContinueOnError)
	// A file rather than an argument, by default. A key on a command line is a key in shell
	// history and in every process listing taken while it ran.
	from := set.String("file", "", "read the key from a file instead of standard input")
	positionals, err := parseAround(set, args)
	if err != nil {
		return err
	}
	if len(positionals) != 1 {
		return errors.New("licence key <name> [--file <path>]")
	}
	name := positionals[0]

	var value string
	if *from != "" {
		raw, err := os.ReadFile(*from)
		if err != nil {
			return err
		}
		value = strings.TrimSpace(string(raw))
	} else {
		fmt.Fprintln(os.Stderr, "reading the key from standard input; it is not echoed anywhere")
		reader := bufio.NewReader(os.Stdin)
		line, err := reader.ReadString('\n')
		if err != nil && line == "" {
			return fmt.Errorf("nothing was given on standard input: %w", err)
		}
		value = strings.TrimSpace(line)
	}

	held, err := openLicences(ctx)
	if err != nil {
		return err
	}
	defer held.Close()

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

	sealed, err := held.Accept(ctx, name, value, func(node string) (string, error) {
		return inv.SealingKeyOf(ctx, node)
	})
	if err != nil {
		if sealed > 0 {
			// Some holders got it and some did not, and the person holding the key is the only
			// one who can finish the job. Saying how far it got is the difference between running
			// this again knowing what it will do and running it hoping.
			return fmt.Errorf(
				"%w\n\n%d holder(s) were sealed before this. Running `licence key %s` again "+
					"with the same key seals the rest and changes nothing for those already done",
				err, sealed, name)
		}
		return err
	}
	// Not echoed back, ever. What is stored is unreadable by whoever holds it, the mesh included,
	// and printing the value here would put the one copy that matters on a terminal.
	fmt.Printf("sealed to %d holder(s). The mesh has discarded the key and cannot read it back\n",
		sealed)
	fmt.Printf("  run `push` to deliver it\n")
	return nil
}

func licenceForget(ctx context.Context, args []string) error {
	if len(args) != 1 {
		return errors.New("licence forget <name>")
	}
	held, err := openLicences(ctx)
	if err != nil {
		return err
	}
	defer held.Close()
	if err := held.Forget(ctx, args[0]); err != nil {
		return err
	}
	// Said plainly, because the mesh cannot do it and pretending otherwise is worse than useless:
	// a licence outliving its holder is a live credential nobody is watching.
	fmt.Printf("%s is forgotten, and every record of who held it with it.\n"+
		"  The key itself is not the mesh's to revoke — do that where the licence was bought\n",
		args[0])
	return nil
}