package main

// The package view (novox/hq ADR 0507 §6, §7; acceptance 1840/AC6): verbs that read the module's states and the
// controller's `declared-packages`, so any instance answers for every node and no machine is asked. A node that is
// off keeps its last values, shown with the time they describe; a node whose packages are over the bus's cap is
// marked not current. A foreign package is listed apart in every answer.

import (
	"encoding/json"
	"fmt"
	"sort"
	"strings"
	"time"
)

// DeclaredPackagesState is the controller's state of the packages each node's modules declare (ADR 0507 §5),
// read through the manifest's `reads`.
const DeclaredPackagesState = "mesh-controller.declared-packages"

// declaredValue is a node's value of `declared-packages`, as the controller writes it.
type declaredValue struct {
	Node     string `json:"node"`
	Packages []struct {
		Package string   `json:"package"`
		Modules []string `json:"modules"`
		Absent  bool     `json:"absent"`
	} `json:"packages"`
}

// nodeInstalled is one node's key of `installed` with its not-current mark.
type nodeInstalled struct {
	Node       string
	Value      InstalledValue
	NotCurrent *NotCurrent
}

func readValue(r StateReader, key string, v any) (bool, error) {
	e, err := r.Get(key)
	if err != nil || e == nil {
		return false, err
	}
	if err := json.Unmarshal(e.Value, v); err != nil {
		return false, fmt.Errorf("%s is not readable: %w", key, err)
	}
	return true, nil
}

// nodeKeys are the node keys of a state (`<node>`), sorted, and the marks (`<node>.not-current`) apart.
func nodeKeys(r StateReader) (nodes []string, marks map[string]bool, err error) {
	keys, err := r.Keys()
	if err != nil {
		return nil, nil, err
	}
	marks = map[string]bool{}
	for _, k := range keys {
		if node, ok := strings.CutSuffix(k, ".not-current"); ok {
			marks[node] = true
			continue
		}
		if !strings.Contains(k, ".") {
			nodes = append(nodes, k)
		}
	}
	sort.Strings(nodes)
	return nodes, marks, nil
}

func (m *Machine) states() error {
	if m.States == nil {
		return fmt.Errorf("the module's states cannot be read here")
	}
	return nil
}

// installedOn is the installed packages of one node, or of every node when node is empty.
func (m *Machine) installedOn(node string) ([]nodeInstalled, error) {
	if err := m.states(); err != nil {
		return nil, err
	}
	r := m.States(StateInstalled)
	nodes, marks, err := nodeKeys(r)
	if err != nil {
		return nil, err
	}
	if node != "" {
		nodes = []string{node}
	}
	var out []nodeInstalled
	for _, n := range nodes {
		ni := nodeInstalled{Node: n}
		found, err := readValue(r, n, &ni.Value)
		if err != nil {
			return nil, err
		}
		if !found {
			if node != "" {
				return nil, fmt.Errorf("no packages of %s are on the bus: its keeper has not written them", node)
			}
			continue
		}
		if marks[n] || node != "" {
			var nc NotCurrent
			if ok, err := readValue(r, NotCurrentKey(n), &nc); err != nil {
				return nil, err
			} else if ok {
				ni.NotCurrent = &nc
			}
		}
		out = append(out, ni)
	}
	return out, nil
}

// declaredOn is what each node's modules declare present, by node and package, with the declaring modules; a
// node the controller holds nothing for is missing.
func (m *Machine) declaredOn(nodes []string) (map[string]map[string][]string, error) {
	r := m.States(DeclaredPackagesState)
	out := map[string]map[string][]string{}
	for _, n := range nodes {
		var v declaredValue
		found, err := readValue(r, n, &v)
		if err != nil {
			return nil, err
		}
		if !found {
			continue
		}
		out[n] = map[string][]string{}
		for _, p := range v.Packages {
			if !p.Absent {
				out[n][p.Package] = p.Modules
			}
		}
	}
	return out, nil
}

// NodeView is one node in the view.
type NodeView struct {
	Node string `json:"node"`
	// At is the time of the transaction that left the node's packages as shown.
	At       time.Time `json:"at"`
	Packages int       `json:"packages"`
	Explicit int       `json:"explicit"`
	// Current is false while the node's packages are over the bus's cap: what is shown is older.
	Current    bool        `json:"current"`
	NotCurrent *NotCurrent `json:"not_current,omitempty"`
	// Undeclared is the packages installed explicitly from a repository that no module assigned to the node
	// declares; null when the controller holds no declaration of the node.
	Undeclared []PackageVersion `json:"undeclared"`
	Foreign    []PackageVersion `json:"foreign"`
}

// Spread is one package across the nodes: its version on each node that has it.
type Spread struct {
	Name     string            `json:"name"`
	Versions map[string]string `json:"versions"`
}

// PackageOnNode is one package on one node.
type PackageOnNode struct {
	Node       string   `json:"node"`
	Installed  bool     `json:"installed"`
	Version    string   `json:"version,omitempty"`
	Explicit   bool     `json:"explicit,omitempty"`
	Repository string   `json:"repository,omitempty"`
	Foreign    bool     `json:"foreign,omitempty"`
	DeclaredBy []string `json:"declared_by"`
	Current    bool     `json:"current"`
}

// Packages is pacman_packages: one package on every node, or the whole view: per node its counts, its explicit
// undeclared packages and its foreign ones; the packages whose versions differ between nodes, and the packages
// on some nodes only, among the packages from a repository (each node's foreign ones are in its own list).
func (m *Machine) Packages(name string, limit int) (map[string]any, error) {
	all, err := m.installedOn("")
	if err != nil {
		return nil, err
	}
	nodes := make([]string, 0, len(all))
	for _, ni := range all {
		nodes = append(nodes, ni.Node)
	}
	declared, err := m.declaredOn(nodes)
	if err != nil {
		return nil, err
	}
	if name != "" {
		on := []PackageOnNode{}
		for _, ni := range all {
			p := PackageOnNode{Node: ni.Node, Current: ni.NotCurrent == nil, DeclaredBy: declared[ni.Node][name]}
			if p.DeclaredBy == nil {
				p.DeclaredBy = []string{}
			}
			for _, ip := range ni.Value.Packages {
				if ip.Name == name {
					p.Installed, p.Version, p.Explicit = true, ip.Version, ip.Explicit
					p.Foreign = ip.Repo == RepoForeign
					if !p.Foreign {
						p.Repository = ip.Repo
					}
				}
			}
			on = append(on, p)
		}
		return map[string]any{"package": name, "nodes": on}, nil
	}
	views := []NodeView{}
	versions := map[string]map[string]string{}
	for _, ni := range all {
		v := NodeView{Node: ni.Node, At: ni.Value.At, Packages: len(ni.Value.Packages), Current: ni.NotCurrent == nil,
			NotCurrent: ni.NotCurrent, Foreign: []PackageVersion{}}
		d, known := declared[ni.Node]
		if known {
			v.Undeclared = []PackageVersion{}
		}
		for _, p := range ni.Value.Packages {
			if p.Explicit {
				v.Explicit++
			}
			if p.Repo == RepoForeign {
				v.Foreign = append(v.Foreign, PackageVersion{p.Name, p.Version})
				continue
			}
			if versions[p.Name] == nil {
				versions[p.Name] = map[string]string{}
			}
			versions[p.Name][ni.Node] = p.Version
			if known && p.Explicit && d[p.Name] == nil {
				v.Undeclared = append(v.Undeclared, PackageVersion{p.Name, p.Version})
			}
		}
		views = append(views, v)
	}
	names := make([]string, 0, len(versions))
	for n := range versions {
		names = append(names, n)
	}
	sort.Strings(names)
	differing, some := []Spread{}, []Spread{}
	for _, n := range names {
		vs := versions[n]
		if len(vs) < len(all) {
			some = append(some, Spread{n, vs})
		}
		seen := map[string]bool{}
		for _, ver := range vs {
			seen[ver] = true
		}
		if len(seen) > 1 {
			differing = append(differing, Spread{n, vs})
		}
	}
	out := map[string]any{"nodes": views}
	for key, list := range map[string][]Spread{"differing": differing, "some_nodes": some} {
		b := bound(key, list, limit)
		out[key] = b[key]
		out[key+"_count"] = b["count"]
		out[key+"_truncated"] = b["truncated"]
	}
	return out, nil
}

// UpdatesView is one node's `updates` with the time its key last changed.
type UpdatesView struct {
	Node      string          `json:"node"`
	Reachable bool            `json:"reachable"`
	Count     int             `json:"count"`
	Packages  []VersionChange `json:"packages"`
	Changed   *time.Time      `json:"changed,omitempty"`
}

// UpdatesFor is pacman_updates: what a full upgrade would change, on one node or on every node, each with when its
// key last changed (the bus's time of the write; the value holds no time of a read, ADR 0289 §4).
func (m *Machine) UpdatesFor(node string) (map[string]any, error) {
	if err := m.states(); err != nil {
		return nil, err
	}
	r := m.States(StateUpdates)
	nodes := []string{node}
	if node == "" {
		var err error
		if nodes, _, err = nodeKeys(r); err != nil {
			return nil, err
		}
	}
	views := []UpdatesView{}
	for _, n := range nodes {
		var v UpdatesValue
		found, err := readValue(r, n, &v)
		if err != nil {
			return nil, err
		}
		if !found {
			if node != "" {
				return nil, fmt.Errorf("no updates of %s are on the bus: its keeper has not written them", node)
			}
			continue
		}
		uv := UpdatesView{Node: n, Reachable: v.Reachable, Count: len(v.Packages), Packages: v.Packages}
		if uv.Packages == nil {
			uv.Packages = []VersionChange{}
		}
		if h, err := r.History(n); err == nil && len(h) > 0 {
			at := h[len(h)-1].At
			uv.Changed = &at
		}
		views = append(views, uv)
	}
	return map[string]any{"nodes": views}, nil
}

// InstalledFrom is pacman_installed from the bus: a node's installed packages with version, reason, repository
// and whether foreign, narrowed by name, reason or foreign, with totals, the time they describe and whether
// they are current.
func (m *Machine) InstalledFrom(node, match, reason string, foreignOnly bool, limit int) (map[string]any, error) {
	ni, err := m.oneNode(node)
	if err != nil {
		return nil, err
	}
	pkgs := []Package{}
	counts := map[string]int{"explicit": 0, "dependency": 0, "foreign": 0}
	for _, ip := range ni.Value.Packages {
		p := Package{Name: ip.Name, Version: ip.Version, Reason: "dependency", Foreign: ip.Repo == RepoForeign}
		if ip.Explicit {
			p.Reason = "explicit"
		}
		if !p.Foreign {
			p.Repository = ip.Repo
		}
		counts[p.Reason]++
		if p.Foreign {
			counts["foreign"]++
		}
		if match != "" && !strings.Contains(p.Name, match) || reason != "" && p.Reason != reason || foreignOnly && !p.Foreign {
			continue
		}
		pkgs = append(pkgs, p)
	}
	out := bound("packages", pkgs, limit)
	out["totals"] = counts
	out["node"], out["at"], out["current"] = ni.Node, ni.Value.At, ni.NotCurrent == nil
	if ni.NotCurrent != nil {
		out["not_current"] = ni.NotCurrent
	}
	return out, nil
}

// ForeignFrom is pacman_foreign from the bus: a node's packages from outside the repositories.
func (m *Machine) ForeignFrom(node string) (map[string]any, error) {
	ni, err := m.oneNode(node)
	if err != nil {
		return nil, err
	}
	pkgs := []PackageVersion{}
	for _, ip := range ni.Value.Packages {
		if ip.Repo == RepoForeign {
			pkgs = append(pkgs, PackageVersion{ip.Name, ip.Version})
		}
	}
	return map[string]any{"node": ni.Node, "count": len(pkgs), "packages": pkgs, "at": ni.Value.At, "current": ni.NotCurrent == nil}, nil
}

// oneNode is the named node's packages, this node's when none is named.
func (m *Machine) oneNode(node string) (nodeInstalled, error) {
	if node == "" {
		node = m.Node
	}
	if node == "" {
		return nodeInstalled{}, fmt.Errorf("node is required: this bundle does not know its own")
	}
	all, err := m.installedOn(node)
	if err != nil {
		return nodeInstalled{}, err
	}
	return all[0], nil
}