package delivery

import (
	"encoding/json"
	"fmt"
	"path"
	"sort"
	"strconv"
	"strings"

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

// Placement of modules on nodes lives in the catalogue (novox/hq ADR 0549): one file per node, `placement/<node>.json`
// in the catalogue repository, changed only by a pull request. At each trunk merge of the catalogue the indexer reads
// the files and writes each node's key `placement.<node>` in its state `placement`, only when it differs, and says
// `placement-changed` naming the node, the revision and the modules added, removed or changed (ADR 0549 §2). The node
// agents, the assigner, the grants part and mesh-config read it (§3); nothing in it is secret.
const (
	// PlacementState is the indexer's state of placements, and PlacementBucket its bucket.
	PlacementState  = "placement"
	PlacementBucket = IndexerModule + "_" + PlacementState
	// PlacementHistory is the revisions the placement bucket keeps per key.
	PlacementHistory = 10
	// PlacementDir is the catalogue's directory of placement files, one `<node>.json` per node.
	PlacementDir = "placement"
	// PlacementChangedEvent is what the indexer says when a node's placement key changed.
	PlacementChangedEvent = "placement-changed"

	placementWord = "placement"

	// CatalogueRepository is the repository whose placement files are the mesh's placement (ADR 0549 §1): the forge bridge
	// reads them at each of its merges, and no other repository's.
	CatalogueRepository = "novox/mesh-catalog"
)

// PlacementKey is the key, in PlacementBucket, of one node's placement: `placement.<node>`.
func PlacementKey(node string) (string, error) {
	if err := checkName("node", node); err != nil {
		return "", err
	}
	return placementWord + "." + node, nil
}

// ParsePlacementKey is the inverse of PlacementKey; it refuses any other key, naming it.
func ParsePlacementKey(key string) (node string, err error) {
	node, ok := strings.CutPrefix(key, placementWord+".")
	if !ok || checkName("node", node) != nil {
		return "", fmt.Errorf("delivery: %q is not a placement key, placement.<node>", key)
	}
	return node, nil
}

// PlacementFile is the path, in the catalogue repository, of one node's placement file.
func PlacementFile(node string) string { return path.Join(PlacementDir, node+".json") }

// PlacementFileNode is the node a catalogue path is the placement file of, and whether it is one: `placement/<node>.json`
// directly under PlacementDir.
func PlacementFileNode(p string) (string, bool) {
	dir, file := path.Split(p)
	node, ok := strings.CutSuffix(file, ".json")
	if path.Clean(dir) != PlacementDir || !ok || checkName("node", node) != nil {
		return "", false
	}
	return node, true
}

// Provider is the module on a node that answers a requirement or holds a seat: a pin's or a binding's provider.
type Provider struct {
	Node   string `json:"node"`
	Module string `json:"module"`
}

// Chosen is p as the composition names a chosen provider.
func (p Provider) Chosen() catalogue.Chosen { return catalogue.Chosen{Node: p.Node, Module: p.Module} }

// PlacedModule is one module placed on the node: the host port each port it declares is published on (by the port the
// software listens on), and, by provision, the provider each of its requirements that keeps data is bound to.
//
// MeshWide and Layer are where the module's things are, as a settings layer's placement holds them (catalogue.Layer's
// Placement: `places`, `accesses`, `networks`, `endpoints`, `expose`, `reach`, `ports`; ADR 0348 §11): the whole mesh's
// layer and this node's, which the controller keeps in its table `placement` (ADR 0549 §6 names it) and composes as two
// layers, the mesh's first. Each node's file repeats the mesh-wide layer of the modules placed on it, so a node reads
// its own key alone. HasLayer says the node has a layer of its own even when it holds no placement, since a layer
// that is there and empty still carries the module's config values (Layers).
type PlacedModule struct {
	Module   string              `json:"module"`
	Ports    map[string]int      `json:"ports,omitempty"`
	Bindings map[string]Provider `json:"bindings,omitempty"`
	MeshWide map[string]any      `json:"mesh-wide,omitempty"`
	HasMesh  bool                `json:"has-mesh-wide,omitempty"`
	Layer    map[string]any      `json:"layer,omitempty"`
	HasLayer bool                `json:"has-layer,omitempty"`
}

// Holding is one seat a module placed on the node holds (catalogue.Held without its node, which is the file's).
type Holding struct {
	Claim  string `json:"claim"`
	Scope  string `json:"scope,omitempty"`
	Module string `json:"module"`
	Site   string `json:"site,omitempty"`
	Kind   string `json:"kind,omitempty"`
}

// Placement is one node's placement: the file the catalogue keeps and, with Revision, the value of its key. Modules are
// in the order the file names them, which is the order the composition reads the node's modules in. Pins is, by
// provision, the provider chosen for the node where more than one could answer.
type Placement struct {
	V        int                 `json:"v"`
	Node     string              `json:"node"`
	Revision string              `json:"revision,omitempty"`
	Decided  NodeDecided         `json:"decided"`
	Modules  []PlacedModule      `json:"modules"`
	Pins     map[string]Provider `json:"pins,omitempty"`
	Holds    []Holding           `json:"holds,omitempty"`
}

// NodeDecided is what a person decides of the node, kept in its placement file (issue 1126's K2: what a person decides
// lives in the catalogue, what the machine observes lives in its record, NodeRecord): where it is dialled (endpoint) and
// its site, whether it is the private network's hub, its address on the private network, the domain its routed names
// are composed under, its operator and agent logins by name and their homes, whether it is adopted rather than
// converged, the modules taken on an adopted node, the tunnel found on it at adoption and, on the hub, the names given
// to that tunnel's peers. The address is a decision written once, at enrolment, by a
// catalogue pull request: nothing allocates it at run time, and CheckPlacements refuses two nodes with one address.
// No secret and no key material: accounts are names, never credentials.
type NodeDecided struct {
	Endpoint     string   `json:"endpoint,omitempty"`
	Site         string   `json:"site,omitempty"`
	Hub          bool     `json:"hub,omitempty"`
	Address      string   `json:"address,omitempty"`
	PublicDomain string   `json:"public-domain,omitempty"`
	Account      string   `json:"account,omitempty"`
	AccountHome  string   `json:"account-home,omitempty"`
	AgentAccount string   `json:"agent-account,omitempty"`
	AgentHome    string   `json:"agent-account-home,omitempty"`
	Adopted      bool     `json:"adopted,omitempty"`
	Taken        []string `json:"taken,omitempty"`
	// Tunnel is the tunnel found on the node when it was adopted, kept as decided then: once the node takes it over it is
	// no longer there to observe. PeerNames is, on the hub, the name a person gave a peer of that tunnel, by its public key.
	Tunnel    *RecordTunnel     `json:"tunnel,omitempty"`
	PeerNames map[string]string `json:"peer-names,omitempty"`
}

func (p Placement) check() error {
	if err := checkName("node", p.Node); err != nil {
		return err
	}
	seen := map[string]bool{}
	for _, m := range p.Modules {
		if err := checkName("module", m.Module); err != nil {
			return err
		}
		if seen[m.Module] {
			return fmt.Errorf("delivery: the placement of %s names %s twice", p.Node, m.Module)
		}
		seen[m.Module] = true
		for port, at := range m.Ports {
			if n, err := strconv.Atoi(port); err != nil || n <= 0 || n > 65535 {
				return fmt.Errorf("delivery: %s's port %q on %s is not a port number", m.Module, port, p.Node)
			}
			if at <= 0 || at > 65535 {
				return fmt.Errorf("delivery: %s's port %s on %s is published on %d, which is not a port number", m.Module, port, p.Node, at)
			}
		}
		for provision, to := range m.Bindings {
			if provision == "" || to.Node == "" || to.Module == "" {
				return fmt.Errorf("delivery: %s on %s has a binding with no provision, node or module", m.Module, p.Node)
			}
		}
	}
	for provision, to := range p.Pins {
		if provision == "" || to.Node == "" || to.Module == "" {
			return fmt.Errorf("delivery: the placement of %s has a pin with no provision, node or module", p.Node)
		}
	}
	for _, h := range p.Holds {
		if h.Claim == "" || !seen[h.Module] {
			return fmt.Errorf("delivery: the placement of %s has %s hold %q, which is not a module placed there or names no seat", p.Node, h.Module, h.Claim)
		}
	}
	return nil
}

// EncodePlacement is p as JSON at Version; it refuses what DecodePlacement refuses.
func EncodePlacement(p Placement) ([]byte, error) {
	if err := p.check(); err != nil {
		return nil, err
	}
	p.V = Version
	return json.Marshal(p)
}

// DecodePlacement reads a placement file or key value; it refuses an unknown version (ErrUnknownVersion), a node or
// module that is not a name, a module named twice, a port that is not a number, a binding or pin naming no provider,
// and a holding by a module not placed on the node.
func DecodePlacement(data []byte) (Placement, error) {
	var p Placement
	if err := decode(data, &p); err != nil {
		return Placement{}, err
	}
	if err := p.check(); err != nil {
		return Placement{}, err
	}
	return p, nil
}

// SamePlacement says whether two placements are the same value, so the indexer writes only when they differ. The
// revision is not compared: a merge that changes no placement writes nothing (ADR 0549 §2).
func SamePlacement(a, b Placement) bool {
	a.Revision, b.Revision = "", ""
	ja, errA := EncodePlacement(a)
	jb, errB := EncodePlacement(b)
	return errA == nil && errB == nil && string(ja) == string(jb)
}

// PlacementChange is what `placement-changed` says: the node, the catalogue revision, and its modules added, removed
// or changed against the placement before.
type PlacementChange struct {
	Node     string   `json:"node"`
	Revision string   `json:"revision"`
	Added    []string `json:"added,omitempty"`
	Removed  []string `json:"removed,omitempty"`
	Changed  []string `json:"changed,omitempty"`
}

// ChangeOf is what changed from before to after on one node; before is the zero Placement for a node new to placement.
// A change of the node's pins or holdings counts as a change of every module placed on it both times, since the
// composition of each may read them.
func ChangeOf(before, after Placement) PlacementChange {
	c := PlacementChange{Node: after.Node, Revision: after.Revision}
	if c.Node == "" {
		c.Node = before.Node
	}
	was := map[string]PlacedModule{}
	for _, m := range before.Modules {
		was[m.Module] = m
	}
	nodeWide := !jsonEqual(before.Pins, after.Pins) || !jsonEqual(before.Holds, after.Holds)
	now := map[string]bool{}
	for _, m := range after.Modules {
		now[m.Module] = true
		old, ok := was[m.Module]
		switch {
		case !ok:
			c.Added = append(c.Added, m.Module)
		case nodeWide || !jsonEqual(old, m):
			c.Changed = append(c.Changed, m.Module)
		}
	}
	for _, m := range before.Modules {
		if !now[m.Module] {
			c.Removed = append(c.Removed, m.Module)
		}
	}
	sort.Strings(c.Added)
	sort.Strings(c.Removed)
	sort.Strings(c.Changed)
	return c
}

func jsonEqual(a, b any) bool {
	ja, _ := json.Marshal(a)
	jb, _ := json.Marshal(b)
	return string(ja) == string(jb)
}

// Assigned is the modules placed on the node, in the file's order (compose.Node's Assigned).
func (p Placement) Assigned() []string {
	out := make([]string, 0, len(p.Modules))
	for _, m := range p.Modules {
		out = append(out, m.Module)
	}
	return out
}

// ChosenPins is the node's pins as the composition reads them (compose.Node's Pins); nil when it has none.
func (p Placement) ChosenPins() map[string]catalogue.Chosen {
	if len(p.Pins) == 0 {
		return nil
	}
	out := make(map[string]catalogue.Chosen, len(p.Pins))
	for provision, to := range p.Pins {
		out[provision] = to.Chosen()
	}
	return out
}

// Bound is, by consumer module and provision, where each binding sends it (compose.Node's Bound); nil when none.
func (p Placement) Bound() map[string]map[string]catalogue.Chosen {
	var out map[string]map[string]catalogue.Chosen
	for _, m := range p.Modules {
		if len(m.Bindings) == 0 {
			continue
		}
		if out == nil {
			out = map[string]map[string]catalogue.Chosen{}
		}
		out[m.Module] = make(map[string]catalogue.Chosen, len(m.Bindings))
		for provision, to := range m.Bindings {
			out[m.Module][provision] = to.Chosen()
		}
	}
	return out
}

// HostPorts is, by module and the port it declares, the host port it is published on (compose.Node's Ports); nil when
// none. The check has refused a port that is not a number, so none is dropped here.
func (p Placement) HostPorts() map[string]map[int]int {
	var out map[string]map[int]int
	for _, m := range p.Modules {
		if len(m.Ports) == 0 {
			continue
		}
		if out == nil {
			out = map[string]map[int]int{}
		}
		out[m.Module] = make(map[int]int, len(m.Ports))
		for port, at := range m.Ports {
			n, _ := strconv.Atoi(port)
			out[m.Module][n] = at
		}
	}
	return out
}

// Layers is one module's settings layers on the node, as the composition reads them (compose.Node's Settings): the
// whole mesh's layer when it has one, then the node's, which carries the module's config values as mesh-config resolved
// them for this node (values, nil when none) beside its placement; a module with no layer and no value has none. This is
// the controller's SettingsFor for a module that takes its config values from mesh-config (issue 664).
func (m PlacedModule) Layers(node string, values map[string]any) []catalogue.Layer {
	var out []catalogue.Layer
	if m.HasMesh || len(m.MeshWide) > 0 {
		out = append(out, catalogue.Layer{From: catalogue.MeshWideLayer, Values: map[string]any{}, Placement: m.MeshWide})
	}
	if m.HasLayer || len(m.Layer) > 0 || len(values) > 0 {
		if values == nil {
			values = map[string]any{}
		}
		out = append(out, catalogue.Layer{From: node, Values: values, Placement: m.Layer})
	}
	return out
}

// Held is the node's holdings as the composition reads them (compose.Input's Holdings rows for this node).
func (p Placement) Held() []catalogue.Held {
	out := make([]catalogue.Held, 0, len(p.Holds))
	for _, h := range p.Holds {
		out = append(out, catalogue.Held{Claim: h.Claim, Scope: h.Scope, Node: p.Node, Module: h.Module, Site: h.Site, Kind: h.Kind})
	}
	return out
}

// CheckPlacements is the catalogue's own check of every placement file (ADR 0549 §1), over the placements by node, the
// modules the catalogue holds and the nodes enrolled. It returns every refusal, in node order, never only the first: a
// placement naming a node not enrolled or a module the catalogue does not hold; two modules of one node on the same host
// port; a pin, binding or holding naming a provider that is not placed where it says; a seat of scope mesh held twice;
// two nodes with one address on the private network; more than one hub.
// A host port a manifest declares without a number and a requirement left unbound are the composition's to find (its
// ForeseenPorts and Unbound), which the catalogue's composition check reads.
func CheckPlacements(placements map[string]Placement, held func(module string) bool, enrolled func(node string) bool) []string {
	var refusals []string
	nodes := make([]string, 0, len(placements))
	for n := range placements {
		nodes = append(nodes, n)
	}
	sort.Strings(nodes)
	placed := func(p Provider) bool {
		other, ok := placements[p.Node]
		if !ok {
			return false
		}
		for _, m := range other.Modules {
			if m.Module == p.Module {
				return true
			}
		}
		return false
	}
	meshSeats := map[string]string{}
	addresses := map[string]string{}
	var hubs []string
	for _, node := range nodes {
		p := placements[node]
		if p.Node != node {
			refusals = append(refusals, fmt.Sprintf("the placement file of %s names the node %q", node, p.Node))
		}
		if a := strings.TrimSpace(p.Decided.Address); a != "" {
			if other, twice := addresses[a]; twice {
				refusals = append(refusals, fmt.Sprintf("%s and %s both have the address %s on the private network", other, node, a))
			}
			addresses[a] = node
		}
		if p.Decided.Hub {
			hubs = append(hubs, node)
		}
		if !enrolled(node) {
			refusals = append(refusals, fmt.Sprintf("%s is not an enrolled node", node))
		}
		hostPorts := map[int]string{}
		for _, m := range p.Modules {
			if !held(m.Module) {
				refusals = append(refusals, fmt.Sprintf("%s: the catalogue holds no module %s", node, m.Module))
			}
			for _, port := range sortedKeys(m.Ports) {
				at := m.Ports[port]
				if other, clash := hostPorts[at]; clash && other != m.Module {
					refusals = append(refusals, fmt.Sprintf("%s: %s and %s are both published on host port %d", node, other, m.Module, at))
				}
				hostPorts[at] = m.Module
			}
			for _, provision := range sortedKeys(m.Bindings) {
				if to := m.Bindings[provision]; !placed(to) {
					refusals = append(refusals, fmt.Sprintf("%s: %s's %s is bound to %s/%s, which is not placed there", node, m.Module, provision, to.Node, to.Module))
				}
			}
		}
		for _, provision := range sortedKeys(p.Pins) {
			if to := p.Pins[provision]; !placed(to) {
				refusals = append(refusals, fmt.Sprintf("%s: the pin of %s names %s/%s, which is not placed there", node, provision, to.Node, to.Module))
			}
		}
		for _, h := range p.Holds {
			if h.Scope != "mesh" {
				continue
			}
			seat := h.Claim + "/" + h.Kind
			if other, twice := meshSeats[seat]; twice {
				refusals = append(refusals, fmt.Sprintf("the seat %s, held once for the mesh, is held on %s and %s", h.Claim, other, node))
			}
			meshSeats[seat] = node
		}
	}
	if len(hubs) > 1 {
		refusals = append(refusals, fmt.Sprintf("the private network has one hub, and %s are each placed as it", strings.Join(hubs, ", ")))
	}
	return refusals
}

func sortedKeys[V any](m map[string]V) []string {
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}