package main

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

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

// The four sources (novox/hq ADR 0348 §2, §3, §9): a module's value on a node resolves, the most specific winning,
// from the default in its manifest, mesh config for the predefined key it falls back to, node config for that key
// on the node, and the module's own value on that node. A value naming no predefined key resolves from its default
// and the module's own value only.

// The states this module keeps, and those it reads (its manifest's `state` and `reads`).
const (
	ValuesState     = "values"
	ResolvedState   = "resolved"
	PredefinedState = "predefined"
	ProposalsState  = "proposals"

	// PlacementRead is the seat mesh-placement's state, held by the assigner (novox/hq ADR 0567 §1, §8): each
	// node's key `placement.<node>` with the modules placed there. It is the one source of which module runs where
	// (issue 1953): the controller's assignments are no longer read.
	PlacementRead = delivery.PlacementRead
	// WantsRead is the assigner's wants, `want.<node>.<module>`: the build each node is to run (ADR 0539 §1).
	WantsRead = delivery.AssignerModule + ".wants"
	// BuildsRead is the builder's builds, `<module>.<fingerprint hex>`: each build's manifest digest (ADR 0525).
	BuildsRead = delivery.BuilderModule + ".builds"
	// ModulesRead is the indexer's modules, `<module>`: the trunk's manifest digest of each module, from whichever
	// repository holds it (ADR 0437 §5, ADR 0478 §9); ManifestsRead its manifests by digest (ADR 0429 §16).
	ModulesRead   = delivery.IndexerModule + ".modules"
	ManifestsRead = delivery.IndexerModule + ".manifests"

	// HistoryLog is the log of every set and clear, with the proven caller and why (ADR 0348 §9).
	HistoryLog = "history"
)

// The sources a resolved value says it came from.
const (
	SourceDefault = "default"
	SourceMesh    = "mesh"
	SourceNode    = "node"
	SourceModule  = "module"
	// SourceUnset is a required value nothing sets: mesh-config answers it unset (ADR 0348 §4).
	SourceUnset = "unset"
)

// The levels a value is set at, and how each is keyed in mesh-config_values (ADR 0348 §9).
const (
	LevelMesh   = "mesh"
	LevelNode   = "node"
	LevelModule = "module"
)

// Level is where a value is set: the mesh, a node, or a module on a node.
type Level struct {
	Kind   string `json:"level"`
	Node   string `json:"node,omitempty"`
	Module string `json:"module,omitempty"`
}

// ValueKey is the level's key for a config key in mesh-config_values.
func (l Level) ValueKey(key string) string {
	switch l.Kind {
	case LevelNode:
		return "node." + l.Node + "." + key
	case LevelModule:
		return "module." + l.Node + "." + l.Module + "." + key
	}
	return "mesh." + key
}

func (l Level) String() string {
	switch l.Kind {
	case LevelNode:
		return "node config on " + l.Node
	case LevelModule:
		return l.Module + "'s own value on " + l.Node
	}
	return "mesh config"
}

// parseValueKey is the level and the config key a key of mesh-config_values names.
func parseValueKey(k string) (Level, string, bool) {
	parts := strings.SplitN(k, ".", 4)
	switch {
	case len(parts) >= 2 && parts[0] == LevelMesh:
		return Level{Kind: LevelMesh}, strings.Join(parts[1:], "."), true
	case len(parts) >= 3 && parts[0] == LevelNode:
		return Level{Kind: LevelNode, Node: parts[1]}, strings.Join(parts[2:], "."), true
	case len(parts) == 4 && parts[0] == LevelModule:
		return Level{Kind: LevelModule, Node: parts[1], Module: parts[2]}, parts[3], true
	}
	return Level{}, "", false
}

// Value is one key of mesh-config_values: the value set, who set it and why, and when.
type Value struct {
	Value json.RawMessage `json:"value"`
	// By is who set it, as proven: the caller, or for a value given at the controller's terminal, who gave it there.
	By string `json:"by"`
	// Via is the bus account the call came from.
	Via string `json:"via"`
	Why string `json:"why"`
	// Approved is who approved it, for a value set on the operator's warrant (ADR 0348 §8, ADR 0277 §15): told from
	// one given at the terminal, which leaves it empty.
	Approved string    `json:"approved,omitempty"`
	At       time.Time `json:"at"`
}

// Resolved is one key of mesh-config_resolved, `<node>.<module>.<key>`: the value a module on a node takes for a
// key, and where it came from. Built from the sources alone, so the same sources give the same bytes and a pass
// over unchanged sources writes nothing.
type Resolved struct {
	Node   string          `json:"node"`
	Module string          `json:"module"`
	Key    string          `json:"key"`
	Value  json.RawMessage `json:"value,omitempty"`
	Source string          `json:"source"`
	// Predefined is the predefined key the value falls back to, when it names one.
	Predefined string `json:"predefined,omitempty"`
	// Required says an unset value is the operator's own to set.
	Required bool `json:"required,omitempty"`
	Trusted  bool `json:"trusted,omitempty"`
}

// ResolvedKey is a resolved value's key in mesh-config_resolved.
func ResolvedKey(node, module, key string) string { return node + "." + module + "." + key }

// Sources is everything a resolution reads: where each module is placed, every module's declarations, the published
// list of predefined keys, and every value set.
type Sources struct {
	Assignments []Assignment
	// Declared is each module's declarations as its manifests declare them: the trunk's, with every key only a wanted
	// build still declares (declarationsOf). It is what a set is judged against.
	Declared map[string]ModuleDeclarations
	// OnNode is, by `<node>.<module>`, the declarations of the build the node's want names laid over the trunk's: what
	// that node resolves. A placed module absent here resolves from Declared.
	OnNode map[string]ModuleDeclarations
	// Unresolved is each placed module whose declarations could not be read, with why: never skipped silently
	// (issue 1953). Its resolved values are kept as they were until its declarations read again.
	Unresolved []Unresolved
	Predefined map[string]Published
	Values     map[string]Value
	// Pulls is what the controller told of each open pull request's declarations, and Kept the approved values held
	// for them (pulls.go); neither is resolved.
	Pulls map[string]PullDecl
	Kept  map[string]KeptValue
}

// Unresolved is a module placed on a node whose values are not resolved, and why.
type Unresolved struct {
	Node   string `json:"node"`
	Module string `json:"module"`
	Why    string `json:"why"`
}

// declarationsOn is the declarations a module on a node resolves from, and whether any are held.
func (s Sources) declarationsOn(node, module string) (ModuleDeclarations, bool) {
	if d, ok := s.OnNode[node+"."+module]; ok {
		return d, true
	}
	d, ok := s.Declared[module]
	return d, ok
}

// unresolved is whether a module on a node is unresolved.
func (s Sources) unresolved(node, module string) bool {
	for _, u := range s.Unresolved {
		if u.Node == node && u.Module == module {
			return true
		}
	}
	return false
}

// Resolve is every placed module's every declared value on its node, keyed as mesh-config_resolved is. A placed
// module with no declarations is in s.Unresolved, said there (sources).
func Resolve(s Sources) map[string]Resolved {
	out := map[string]Resolved{}
	for _, a := range s.Assignments {
		decl, ok := s.declarationsOn(a.Node, a.Module)
		if !ok {
			continue
		}
		for _, key := range sortedKeys(decl.Config) {
			r := resolveOne(s, a.Node, a.Module, key, decl.Config[key])
			out[ResolvedKey(a.Node, a.Module, key)] = r
		}
	}
	return out
}

func resolveOne(s Sources, node, module, key string, d Declaration) Resolved {
	r := Resolved{Node: node, Module: module, Key: key, Source: SourceUnset, Predefined: d.Predefined,
		Required: d.Required, Trusted: d.Trusted}
	if d.HasDefault() {
		r.Value, r.Source = compact(d.Default), SourceDefault
	}
	if d.Predefined != "" {
		if p, ok := s.Predefined[d.Predefined]; ok && p.Trusted {
			r.Trusted = true
		}
		if v, ok := s.Values[Level{Kind: LevelMesh}.ValueKey(d.Predefined)]; ok {
			r.Value, r.Source = compact(v.Value), SourceMesh
		}
		if v, ok := s.Values[Level{Kind: LevelNode, Node: node}.ValueKey(d.Predefined)]; ok {
			r.Value, r.Source = compact(v.Value), SourceNode
		}
	}
	if v, ok := s.Values[Level{Kind: LevelModule, Node: node, Module: module}.ValueKey(key)]; ok {
		r.Value, r.Source = compact(v.Value), SourceModule
	}
	return r
}

// compact is a JSON value encoded the one way: objects' keys sorted, no spaces.
func compact(raw json.RawMessage) json.RawMessage {
	var v any
	if err := json.Unmarshal(raw, &v); err != nil {
		return raw
	}
	out, err := json.Marshal(v)
	if err != nil {
		return raw
	}
	return out
}

// Moved is one resolved value that changed: a module on a node whose value for a key moved, from what to what.
type Moved struct {
	Node   string          `json:"node"`
	Module string          `json:"module"`
	Key    string          `json:"key"`
	From   json.RawMessage `json:"from,omitempty"`
	To     json.RawMessage `json:"to,omitempty"`
	Source string          `json:"source"`
	// Gone says the module no longer takes the key there: no longer placed, or no longer declared.
	Gone bool `json:"gone,omitempty"`
}

// diff is what moved between the resolved values held and those wanted, in key order.
func diff(held, want map[string]Resolved) []Moved {
	var out []Moved
	for _, k := range sortedKeys(want) {
		w := want[k]
		h, had := held[k]
		if had && string(encodeResolved(h)) == string(encodeResolved(w)) {
			continue
		}
		m := Moved{Node: w.Node, Module: w.Module, Key: w.Key, To: w.Value, Source: w.Source}
		if had {
			m.From = h.Value
		}
		out = append(out, m)
	}
	for _, k := range sortedKeys(held) {
		if _, ok := want[k]; !ok {
			h := held[k]
			out = append(out, Moved{Node: h.Node, Module: h.Module, Key: h.Key, From: h.Value, Gone: true})
		}
	}
	sort.SliceStable(out, func(i, j int) bool {
		return ResolvedKey(out[i].Node, out[i].Module, out[i].Key) < ResolvedKey(out[j].Node, out[j].Module, out[j].Key)
	})
	return out
}

func encodeResolved(r Resolved) []byte {
	raw, err := json.Marshal(r)
	if err != nil {
		panic(fmt.Sprintf("a resolved value cannot be encoded: %v", err))
	}
	return raw
}