package compose

import (
	"fmt"
	"slices"

	"git.novox.be/novox/mesh-sdk/go/catalogue"
)

// LicenceProvision is what a module requires in order to be given a licence (the controller's licences.Provision).
const LicenceProvision = "model-access"

// Resolved is what one node should run, from what was assigned to it, with the settings of everything that resolved.
type Resolved struct {
	Plan     catalogue.Resolution
	Settings catalogue.SettingsBy
	// Foreseen are the needs composed with a stand-in for a credential the next send makes (or holds with no value given
	// here), as "<module> on <node> needs <provision> from <provider>". Nothing was made.
	Foreseen []string
	// NotGiven are the words of each credential only a person gives that nobody has: the consumer still resolves without it
	// (novox/hq ADR 0337 clause 4).
	NotGiven []string
}

// Resolve works out everything a node should run, from what was assigned to it (the controller's planFor, plan.go): the
// resolution over the rest of the mesh, the credential of each thing the node takes from elsewhere, and the settings of
// every module that resolved. It makes and writes nothing: a credential not held is composed with a stand-in and named
// foreseen, one only a person gives and nobody has is left out and said, one the send would refuse is refused with the
// controller's words. A failure to compose the node's own modules is an error that satisfies IsUnresolvable, told apart
// from an unreadable Input (novox/hq 04-ISSUES/152).
func Resolve(in Input, node string) (Resolved, error) {
	return newComposer(in).planFor(node)
}

// IsUnresolvable reports whether err is a node's own set failing to compose, rather than the mesh being unable to answer.
func IsUnresolvable(err error) bool { return unresolvable(err) }

// planFor is the controller's planFor.
func (c *composer) planFor(nodeName string) (Resolved, error) {
	resolved, err := c.resolution(nodeName)
	if err != nil {
		return Resolved{}, err
	}
	node, err := c.in.node(nodeName)
	if err != nil {
		return Resolved{}, err
	}
	shelf := c.shelfFor(node)
	var out Resolved

	// The credential for each thing this node takes from elsewhere.
	for i, n := range resolved.Needs {
		// Issued for this holder alone and kept by the vault (issue 757).
		resolved.Needs[i].IssuedToHolder = issuedToHolder(shelf, n)
		resolved.Needs[i].ProviderMoved = providerMoved(shelf, n)
		if n.ByRecord {
			// Answered by something the mesh holds, so there is no pair-wise secret between two machines.
			licence, _ := c.licence(n.From)
			if licence.Keys == nil {
				// The keys are not given: composed with a stand-in and named, not failed for a value only a send reads.
				resolved.Needs[i].Sealed = catalogue.ForeseenSealed
				out.Foreseen = append(out.Foreseen, fmt.Sprintf("%s on %s needs %s from %s", n.For, nodeName, n.Name, n.From))
			} else {
				// Given, and none for this holder: the mesh holds none.
				resolved.Needs[i].Sealed = licence.Keys[Holder{Node: nodeName, Module: n.For}]
			}
			// If this holder is the licence's manager, hand it the manager node's PUBLIC sealing key in its bound facts
			// (novox/hq ADR 0050).
			if pub := c.managerPublicKeyFor(licence, nodeName, n.For); pub != "" {
				serves := map[string]any{}
				for k, v := range resolved.Needs[i].Serves {
					serves[k] = v
				}
				serves["manager_public_key"] = pub
				resolved.Needs[i].Serves = serves
				// The manager holder: its empty pre-adoption refresh token is a waiting state, not a missing consumer key.
				resolved.Needs[i].Manager = true
			}
			continue
		}
		cred, held := c.credential(n, nodeName)
		_, outside := issuedOutsideBy(shelf, n)
		switch {
		case cred.State == CredentialRefused:
			// Said rather than skipped. A machine that resolves cleanly and receives no credential is one that will fail to
			// authenticate at some later, less obvious moment.
			return Resolved{}, fmt.Errorf("%s on %s needs %s from %s and no credential could be made for it: %s",
				n.For, nodeName, n.Name, n.From, cred.Why)
		case cred.State == CredentialNotGiven, outside && !(held && cred.State == CredentialHeld):
			// Not given, and the rest of the consumer runs (ADR 0337 clause 4): no credential file, so the module can tell
			// it was not given; nothing the mesh made stands in for it.
			why := cred.Why
			if why == "" {
				why = "nobody gave it"
			}
			out.NotGiven = append(out.NotGiven, fmt.Sprintf("%s on %s holds no %s from %s: %s", n.For, nodeName, n.Name, n.From, why))
			continue
		case cred.State == CredentialHeld && cred.Sealed != "":
			resolved.Needs[i].Sealed = cred.Sealed
		default:
			// Held with no value here, or none held: the next send makes it (or reads it), and a stand-in is composed.
			resolved.Needs[i].Sealed = catalogue.ForeseenSealed
			out.Foreseen = append(out.Foreseen, fmt.Sprintf("%s on %s needs %s from %s", n.For, nodeName, n.Name, n.From))
		}
	}

	// Settings for everything that resolved, including modules nobody assigned directly: a requirement pulled in by
	// something else is still configurable.
	settings := catalogue.SettingsBy{}
	for _, m := range resolved.Modules {
		layers := node.Settings[m.Module]
		if len(layers) == 0 {
			continue
		}
		settings[m.Module] = append([]catalogue.Layer(nil), layers...)
	}
	out.Plan, out.Settings = resolved, settings
	return out, nil
}

// credential is how the pair credential of one need stands in the Input, and whether the Input names it at all.
func (c *composer) credential(n catalogue.Needed, consumer string) (Credential, bool) {
	for _, cr := range c.in.Credentials {
		if cr.Provision == n.Name && cr.Consumer == consumer && cr.ConsumerModule == n.For && cr.Provider == n.From && cr.Local == n.Local {
			return cr, true
		}
	}
	return Credential{State: CredentialWouldMake}, false
}

// licence is the licence of that name.
func (c *composer) licence(name string) (Licence, bool) {
	for _, l := range c.in.Licences {
		if l.Name == name {
			return l, true
		}
	}
	return Licence{}, false
}

// managerPublicKeyFor is the manager node's public sealing key, but only when (node, module) is the licence's manager holder
// and empty otherwise (plan.go managerPublicKeyFor): delivered to the manager module in its bound facts so it can re-seal a
// rotated refresh token to this node (novox/hq ADR 0050), and to no consumer.
func (c *composer) managerPublicKeyFor(l Licence, node, module string) string {
	if l.Manager == (Holder{}) || node != l.Manager.Node || module != l.Manager.Module {
		return ""
	}
	n, err := c.in.node(node)
	if err != nil {
		return ""
	}
	return n.SealingKey
}

// issuedOutsideBy is whether a need's provision is offered by its provider with a credential issued outside the mesh
// (novox/hq ADR 0337), and that provider module: the one answering it when known, else any that offers it so.
func issuedOutsideBy(shelf map[string]catalogue.Manifest, n catalogue.Needed) (string, bool) {
	if n.Module != "" {
		if m, known := shelf[n.Module]; known {
			return n.Module, m.IssuedOutsideOf(n.Name)
		}
	}
	return catalogue.OffersIssuedOutside(shelf, n.Name)
}

// issuedToHolder is whether the vault keeps a need's credential for its holder alone (issues 749, 757 and 779).
func issuedToHolder(shelf map[string]catalogue.Manifest, n catalogue.Needed) bool {
	if n.ByRecord || n.Module == "" {
		return false
	}
	provider, known := shelf[n.Module]
	if !known || !movedProvider(provider) {
		return false
	}
	if _, issued := provider.IssuedCredentialOf(n.Name); issued {
		return true
	}
	return provider.CredentialFormOf(n.Name) == catalogue.CredentialFormPair
}

// providerMoved is whether a need is answered by a module marked moved (issue 788), or by one whose offer of the provision
// says the provider helper answers it (issue 792).
func providerMoved(shelf map[string]catalogue.Manifest, n catalogue.Needed) bool {
	if n.ByRecord || n.Module == "" {
		return false
	}
	provider, known := shelf[n.Module]
	return known && (movedProvider(provider) || provider.AnsweredByHelperFor(n.Name))
}

// movedProvider is whether a provider's credentials are the vault's: the module is marked moved, or it holds the
// mesh-vault seat (issue 793).
func movedProvider(m catalogue.Manifest) bool {
	return m.Moved || slices.ContainsFunc(m.Claims, func(c catalogue.Claim) bool { return c.Name == "mesh-vault" })
}

// resolution works out what one node should run, from what was assigned to it: the controller's planFor up to and
// including the resolution (plan.go planFor), and no further. A failure to compose the node's own modules is wrapped as
// notResolvable; every other failure is returned as it is.
func (c *composer) resolution(nodeName string) (catalogue.Resolution, error) {
	node, err := c.in.node(nodeName)
	if err != nil {
		return catalogue.Resolution{}, err
	}
	shelf := c.shelfFor(node)
	world, _, _, err := c.theRestOfTheMesh(nodeName)
	if err != nil {
		return catalogue.Resolution{}, err
	}
	world.Pinned = node.Pins
	// Where each of its consumers of a provision that keeps data was last sent (novox/hq ADR 0232).
	world.Bound = node.Bound

	onNetwork, err := c.whereEveryoneIs()
	if err != nil {
		return catalogue.Resolution{}, err
	}

	// What this mesh can answer with a record rather than a machine, and which record each of this node's modules was
	// put on.
	world.Licences, world.Using = c.licencesFor(nodeName)

	resolved, err := catalogue.Resolve(shelf, node.Assigned,
		catalogue.Node{Name: nodeName, Site: node.Place.Site, Capabilities: node.Capabilities,
			At: onNetwork[nodeName], PublicDomain: node.PublicDomain,
			Account: node.Account, AccountHome: node.AccountHome,
			AgentAccount: node.AgentAccount, AgentAccountHome: node.AgentAccountHome}, world)
	if err != nil {
		// The node's own set does not compose: the only failure a mesh-wide gatherer may pass over.
		return catalogue.Resolution{}, notResolvable{err}
	}
	return resolved, nil
}

// shelfFor is the catalogue as one node composes its own set: the Input's, with each recorded or core module the node keeps at the
// build it runs put in place of the current one (plan.go keepRecorded). A copy: the Input's catalogue, and so every other node's
// resolution, is untouched.
func (c *composer) shelfFor(node Node) map[string]catalogue.Manifest {
	if len(node.Kept) == 0 {
		return c.in.Catalogue
	}
	shelf := make(map[string]catalogue.Manifest, len(c.in.Catalogue)+len(node.Kept))
	for name, m := range c.in.Catalogue {
		shelf[name] = m
	}
	for name, m := range node.Kept {
		shelf[name] = m
	}
	return shelf
}

// licencesFor is what this node can be answered with by record, and what it was put on. A mesh with no licences at all
// is the ordinary case and not an error.
func (c *composer) licencesFor(node string) (map[string][]catalogue.Record, map[string]map[string]catalogue.Record) {
	all := c.in.Licences
	if len(all) == 0 {
		return nil, nil
	}
	offered := map[string][]catalogue.Record{}
	byName := map[string]catalogue.Record{}
	for _, one := range all {
		record := catalogue.Record{Name: one.Name, Serves: one.Serves}
		offered[LicenceProvision] = append(offered[LicenceProvision], record)
		byName[one.Name] = record
	}
	using := map[string]map[string]catalogue.Record{}
	for _, one := range all {
		for _, h := range one.Holders {
			if h.Node != node {
				continue
			}
			if using[h.Module] == nil {
				using[h.Module] = map[string]catalogue.Record{}
			}
			using[h.Module][LicenceProvision] = byName[one.Name]
		}
	}
	return offered, using
}