package main

// The controller's condition events, read in this one place (novox/hq to-be 45 §2).
//
// **The contract this reads, and every assumption it makes about it**, because the controller's
// side was built at the same time from the same design and the design names the events and the
// fields but not their spelling on the wire:
//
//   - The events are the mesh-controller seat's own: `condition-raised`, `condition-changed` and
//     `condition-cleared`, consumed as `mesh-controller.<event>` (subject
//     `mesh.seat.mesh-controller.event.<event>`), exactly as `applied` and `built-before` are.
//   - The body is the condition as the store holds it, one JSON object, with the field names of the
//     design's table in kebab-case: key, kind, subject, severity, summary, evidence, source, raised,
//     last-observed, observations, tried, resolver, silenced, epoch. snake_case and camelCase
//     spellings of the two-word names are read too.
//   - `subject` is an object {scope, id, machine}; a plain string is read as well.
//   - `severity` is `urgent` or `warning`. Anything else is not guessed: the event is unreadable.
//   - `silenced` is absent, null, or an object {until, by, why}; `until` in the past is not silenced.
//   - Times are RFC 3339.
//   - `headline`, `explanation` and `resolved` are the plain words the operator reads (novox/hq ADR
//     0253): a condition from a controller older than them has none, and is said from its summary.
//   - `needs` is what the operator does, empty for nothing (the explanation opens with the verdict);
//     `actions` are the answers a notification offers, each {label, verb, machine, arguments}.
//   - `key` is `<scope>.<id>.<kind>`. When it is absent it is made from subject and kind; when
//     neither gives one the event is unreadable.
//   - A cleared event carries the condition as last held, and may add `cleared` (its time).
//   - Every event carries `at`, when the transition happened (the controller's conditions.Event).
//     It is how this holder tells news from history: a stream replays what it holds to a consumer
//     that is new or was away, and an event's delivery time says nothing about when it happened.
//   - The `conditions` verb of the controller's seat answers `{conditions: [...], open, note}`, each
//     entry the condition as the store holds it — the same shape as an event's body.
//
// An event this cannot read is refused by name — which event, which field, why — counted, said in
// the status and in the log, and told to the operator; never read as an empty condition.

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

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

// The events, by their local names under the controller's seat.
const (
	EventRaised  = "condition-raised"
	EventChanged = "condition-changed"
	EventCleared = "condition-cleared"
	// ControllerSeat is the role the events are stated under.
	ControllerSeat = "mesh-controller"
)

// Severities: two levels, no more (to-be 45 §2).
const (
	Urgent  = "urgent"
	Warning = "warning"
)

// Condition is what this holder needs of one.
type Condition struct {
	Key         string
	Kind        string
	Scope       string
	ID          string
	Machine     string
	Severity    string
	Summary     string
	Headline    string
	Explanation string
	Resolved    string
	Needs       string
	Actions     []Action
	Source      string
	// Publisher is the module that said the condition on the operator channel's one subject; empty for the
	// controller's own, which a reading of the controller's conditions may end.
	Publisher    string
	Resolver     string
	Raised       time.Time
	LastObserved time.Time
	Observations int
	SilencedTill time.Time
	SilencedWhy  string
	Cleared      time.Time
	// At is when the transition the event says happened; zero for a condition read from the open set.
	At time.Time
}

// When is the event's own time: `at`; without it, the clearing's or the raising's time; without
// those, zero — and a zero time is read as now by the holder, never as old.
func (c Condition) When(event string) time.Time {
	switch {
	case !c.At.IsZero():
		return c.At
	case event == EventCleared:
		return c.Cleared
	case event == EventRaised:
		return c.Raised
	}
	return time.Time{}
}

// SubjectWords is the subject as a person reads it: "machine ace", "plan 41", "provider keycloak".
func (c Condition) SubjectWords() string {
	parts := []string{}
	if c.Scope != "" {
		parts = append(parts, c.Scope)
	}
	if c.ID != "" {
		parts = append(parts, c.ID)
	}
	if c.Machine != "" && c.Machine != c.ID {
		parts = append(parts, "on "+c.Machine)
	}
	return strings.Join(parts, " ")
}

// SilencedAt says whether the condition's messages are stopped at that moment.
func (c Condition) SilencedAt(now time.Time) bool {
	return !c.SilencedTill.IsZero() && now.Before(c.SilencedTill)
}

// eventOf is the local event name of an envelope's key: `mesh-controller.condition-raised` is
// `condition-raised`. Anything not of the controller's seat is not a condition event.
func eventOf(key string) (string, bool) { return eventOfSeat(key, ControllerSeat) }

// eventOfSeat is eventOf for the seat the take-over key says is followed: the controller's, or the keeper's (ADR 0564 clause 9).
func eventOfSeat(key, seat string) (string, bool) {
	emitter, event, ok := strings.Cut(key, ".")
	if !ok || emitter != seat {
		return "", false
	}
	switch event {
	case EventRaised, EventChanged, EventCleared:
		return event, true
	}
	return "", false
}

// DecodeCondition reads one condition event's body.
func DecodeCondition(event string, body []byte) (Condition, error) {
	var raw map[string]json.RawMessage
	if err := json.Unmarshal(body, &raw); err != nil {
		return Condition{}, fmt.Errorf("%s: the body is not a JSON object: %v", event, err)
	}
	if raw == nil {
		return Condition{}, fmt.Errorf("%s: the body is null", event)
	}
	var c Condition
	var err error
	str := func(names ...string) string {
		if err != nil {
			return ""
		}
		for _, n := range names {
			v, ok := raw[n]
			if !ok || string(v) == "null" {
				continue
			}
			var s string
			if e := json.Unmarshal(v, &s); e != nil {
				err = fmt.Errorf("%s: %s is not a string", event, n)
				return ""
			}
			return strings.TrimSpace(s)
		}
		return ""
	}
	when := func(names ...string) time.Time {
		s := str(names...)
		if s == "" || err != nil {
			return time.Time{}
		}
		t, e := time.Parse(time.RFC3339Nano, s)
		if e != nil {
			err = fmt.Errorf("%s: %s is not an RFC 3339 time: %q", event, names[0], s)
		}
		return t
	}
	c.Key = str("key")
	c.Kind = str("kind")
	c.Severity = str("severity")
	c.Summary = str("summary")
	c.Headline = str("headline")
	c.Explanation = str("explanation")
	c.Resolved = str("resolved")
	c.Needs = str("needs")
	if v, ok := raw["actions"]; ok && string(v) != "null" {
		if e := json.Unmarshal(v, &c.Actions); e != nil {
			return Condition{}, fmt.Errorf("%s: actions is not a list of {label, verb, machine, arguments}", event)
		}
	}
	c.Resolver = str("resolver")
	c.Raised = when("raised")
	c.LastObserved = when("last-observed", "last_observed", "lastObserved")
	c.Cleared = when("cleared")
	c.At = when("at")
	if err != nil {
		return Condition{}, err
	}
	// source: a string, or an object naming the row, probe or event.
	if v, ok := raw["source"]; ok && string(v) != "null" {
		var s string
		if json.Unmarshal(v, &s) == nil {
			c.Source = s
		} else {
			var o map[string]any
			if json.Unmarshal(v, &o) == nil {
				for _, k := range []string{"row", "probe", "event", "name", "id"} {
					if s, ok := o[k].(string); ok && s != "" {
						c.Source = s
						break
					}
				}
			}
		}
	}
	for _, n := range []string{"observations", "count"} {
		if v, ok := raw[n]; ok && string(v) != "null" {
			var f float64
			if json.Unmarshal(v, &f) != nil {
				return Condition{}, fmt.Errorf("%s: %s is not a number", event, n)
			}
			c.Observations = int(f)
			break
		}
	}
	if v, ok := raw["subject"]; ok && string(v) != "null" {
		var s string
		if json.Unmarshal(v, &s) == nil {
			c.ID = strings.TrimSpace(s)
		} else {
			var o struct {
				Scope   string `json:"scope"`
				ID      string `json:"id"`
				Machine string `json:"machine"`
				Node    string `json:"node"`
			}
			if e := json.Unmarshal(v, &o); e != nil {
				return Condition{}, fmt.Errorf("%s: subject is neither a string nor {scope, id, machine}", event)
			}
			c.Scope, c.ID, c.Machine = o.Scope, o.ID, o.Machine
			if c.Machine == "" {
				c.Machine = o.Node
			}
		}
	}
	if v, ok := raw["silenced"]; ok && string(v) != "null" && string(v) != "{}" && string(v) != `""` && string(v) != "false" {
		var o struct {
			Until string `json:"until"`
			Why   string `json:"why"`
		}
		if e := json.Unmarshal(v, &o); e != nil {
			return Condition{}, fmt.Errorf("%s: silenced is not {until, by, why}", event)
		}
		if o.Until != "" {
			t, e := time.Parse(time.RFC3339Nano, o.Until)
			if e != nil {
				return Condition{}, fmt.Errorf("%s: silenced.until is not an RFC 3339 time: %q", event, o.Until)
			}
			c.SilencedTill = t
		}
		c.SilencedWhy = o.Why
	}
	if c.Key == "" && c.Scope != "" && c.ID != "" && c.Kind != "" {
		c.Key = c.Scope + "." + c.ID + "." + c.Kind
	}
	if c.Key == "" {
		return Condition{}, fmt.Errorf("%s: no key, and no subject and kind to make one from", event)
	}
	if c.Scope == "" || c.ID == "" || c.Kind == "" {
		// The key names them (`<scope>.<id>.<kind>`, the id itself possibly dotted).
		parts := strings.Split(c.Key, ".")
		if len(parts) >= 3 {
			if c.Scope == "" {
				c.Scope = parts[0]
			}
			if c.Kind == "" {
				c.Kind = parts[len(parts)-1]
			}
			if c.ID == "" {
				c.ID = strings.Join(parts[1:len(parts)-1], ".")
			}
		}
	}
	switch c.Severity {
	case Urgent, Warning:
	case "":
		if event != EventCleared {
			return Condition{}, fmt.Errorf("%s %s: no severity", event, c.Key)
		}
	default:
		return Condition{}, fmt.Errorf("%s %s: severity %q is neither urgent nor warning", event, c.Key, c.Severity)
	}
	if c.Summary == "" && event != EventCleared {
		return Condition{}, fmt.Errorf("%s %s: no summary", event, c.Key)
	}
	return c, nil
}

// DecodeOpen reads the controller's `conditions` answer — what is open now — bare, inside the
// runtime's `{answer}` or `{output}`, inside a tool reply's text content, or as a JSON string. An
// answer without a `conditions` list is refused: an empty open set is said, never assumed.
func DecodeOpen(raw json.RawMessage) ([]Condition, error) {
	var m map[string]json.RawMessage
	if err := json.Unmarshal(raw, &m); err != nil {
		var s string
		if json.Unmarshal(raw, &s) == nil {
			return DecodeOpen(json.RawMessage(s))
		}
		return nil, fmt.Errorf("the conditions answer is not JSON")
	}
	if list, ok := m["conditions"]; ok {
		var items []json.RawMessage
		if string(list) != "null" {
			if err := json.Unmarshal(list, &items); err != nil {
				return nil, fmt.Errorf("the conditions answer's conditions is not a list")
			}
		}
		out := make([]Condition, 0, len(items))
		for _, it := range items {
			c, err := DecodeCondition("conditions", it)
			if err != nil {
				return nil, err
			}
			out = append(out, c)
		}
		return out, nil
	}
	for _, k := range []string{"answer", "output"} {
		if v, ok := m[k]; ok && string(v) != "null" {
			return DecodeOpen(v)
		}
	}
	if v, ok := m["content"]; ok {
		var content []struct {
			Text string `json:"text"`
		}
		var e struct {
			IsError bool `json:"isError"`
		}
		_ = json.Unmarshal(raw, &e)
		if json.Unmarshal(v, &content) == nil && len(content) > 0 {
			if e.IsError {
				return nil, fmt.Errorf("the controller refused: %s", content[0].Text)
			}
			return DecodeOpen(json.RawMessage(content[0].Text))
		}
	}
	return nil, fmt.Errorf("the conditions answer lists no conditions")
}

// ConditionVerb is the verb a module says a condition with: `mesh.seat.operator-channel.accept.condition.<publisher>`
// (novox/hq ADR 0437 §9).
const ConditionVerb = "condition"

// takeCondition takes one condition a module said on the seat's one subject. It is decided exactly as the
// controller's conditions are, by Condition: there is no second path. The publisher is the subject's last
// token, which the bus grants that module alone, so it is not compared with the condition's key. A body that is
// not a condition in the SDK's layout is logged by publisher, taken and dropped.
func (h *Holder) takeCondition(publisher string, body []byte) {
	sc, err := asks.DecodeCondition(body)
	if err != nil {
		h.Logf("[messenger] a condition from %s was taken and dropped: %v", publisher, err)
		return
	}
	c := Condition{Key: sc.Key, Scope: sc.Subject.Scope, ID: sc.Subject.ID, Machine: sc.Subject.Machine,
		Severity: sc.Severity, Summary: sc.Summary, Headline: sc.Headline, Explanation: sc.Explanation,
		Resolved: sc.Resolved, Needs: sc.Needs, Source: publisher, Publisher: publisher}
	if i := strings.LastIndex(sc.Key, "."); i >= 0 {
		c.Kind = sc.Key[i+1:]
	}
	for _, a := range sc.Actions {
		c.Actions = append(c.Actions, Action{Label: a.Label, Verb: a.Verb, Machine: a.Machine, Arguments: a.Arguments})
	}
	if sc.State == asks.StateCleared {
		h.Condition(EventCleared, c)
		return
	}
	h.Condition(EventRaised, c)
}