package conditions

// Plain words (novox/hq ADR 0253): **a condition carries what the operator reads, in plain words, beside
// what an agent reads.** The summary is one line in the mesh's words for whoever looks closer — it names
// plans, commits and the verbs that act, and stays so. The operator reads a notification between other
// work: a popup that said "the walk of novox/mesh-catalog a6385479 has waited 56m0s for mesh-delivery's
// word to start: `mesh-delivery.show` …" was a wall of identifiers nobody could act on. So every condition
// also carries:
//
//   - a **headline**: a few plain words naming the thing and what is wrong ("openrazer not running on
//     g14"), the title of every message about it;
//   - an **explanation**: one or two plain sentences — what happened, what it means for the operator,
//     and whether they need to do anything;
//   - a **resolved line**: the one short line said when it clears ("openrazer runs again on g14");
//   - a **verdict**, which every explanation opens with: "Nothing for you to do." or "Needs you:" and one
//     concrete thing the operator can do themselves (needs). Never "have an agent …": the operator is not
//     asked to open a session to understand or answer a notification;
//   - **actions**: what the operator may answer from the notification itself (Release, Stop, Restart,
//     Silence), each the seat verb the operator channel calls when it is chosen, naming the operator.
//
// They are made here, where the condition is made, so every channel gets them — the desktop today,
// others later — and none has to guess what a key means. A producer may say them itself; otherwise the
// wording registered for its kind says them; otherwise a plain sentence made from its scope does, and a
// test suite is told (Unworded) so the kind gets words of its own. Each is held to the plain rule (Plain):
// no identifiers, hashes, keys, verb syntax, markup or clock times — a message names no time of its own,
// since the channel says when, in the operator's time.

import (
	"fmt"
	"regexp"
	"strings"
	"sync"

	"github.com/novox/mesh-controller/internal/outward"
)

// Words are what the operator reads of a condition. Explanation is said after the verdict, which
// plainly writes from Needs: empty is "Nothing for you to do.", else "Needs you: " and Needs.
type Words struct {
	Headline    string
	Explanation string
	Resolved    string
	Needs       string
	Actions     []Action
}

// Action is one answer the operator may give from a notification: a label, and the seat verb the
// operator channel calls with these arguments (and a why naming the operator and the label) when it is
// chosen. Machine is set for a seat every machine holds. An argument "why" given empty is the operator
// channel's to fill: it names the operator, the channel and the label chosen.
type Action struct {
	Label     string            `json:"label"`
	Verb      string            `json:"verb"`
	Machine   string            `json:"machine,omitempty"`
	Arguments map[string]string `json:"arguments,omitempty"`
}

// The two verdicts an explanation opens with.
const (
	NothingToDo = "Nothing for you to do."
	NeedsYou    = "Needs you:"
)

// SilenceAction is the action that stops a condition's messages for a week, with the operator's why: the
// answer to a condition the operator decided to live with.
func SilenceAction(key string) Action {
	return Action{Label: "Silence for a week", Verb: "mesh-controller.conditions",
		Arguments: map[string]string{"silence": key, "for": "7d", "why": ""}}
}

// Bounds of the plain words: a headline fits a notification's title line, an explanation two sentences.
const (
	HeadlineMax    = 60
	ExplanationMax = 420
	NeedsMax       = 120
)

var (
	wordingsMu sync.RWMutex
	wordings   = map[string]func(Observation) Words{}
)

// Wording registers the plain words of one condition kind.
func Wording(kind string, words func(Observation) Words) {
	wordingsMu.Lock()
	defer wordingsMu.Unlock()
	wordings[kind] = words
}

// Worded says whether a kind has words of its own.
func Worded(kind string) bool {
	wordingsMu.RLock()
	defer wordingsMu.RUnlock()
	_, ok := wordings[kind]
	return ok
}

// Unworded is told of every observation said in borrowed words: its kind has none registered, or the
// words it was given break the plain rule. The keeper says it plainly anyway; a test suite sets this to
// fail the producer.
var Unworded func(o Observation, why string)

// The plain rule's shapes.
var (
	hexID      = regexp.MustCompile(`\b[0-9a-f]{7,40}\b`)
	numberedID = regexp.MustCompile(`\b[a-z]+-[0-9]{6,}\b`)
	dotted     = regexp.MustCompile(`\b[a-z][a-z0-9_-]*\.[a-z][a-z0-9_-]*\b`)
	goDuration = regexp.MustCompile(`\b[0-9]+(h[0-9]+m|m[0-9]+s|h[0-9]+m[0-9]+s)\b|\b[0-9]+(\.[0-9]+)?(ns|ms|µs)\b`)
	clockTime  = regexp.MustCompile(`\b[0-9]{1,2}:[0-9]{2}\b|\b[0-9]{4}-[0-9]{2}-[0-9]{2}\b|\bUTC\b`)
	flag       = regexp.MustCompile(`(^|\s)--?[a-z]`)
	agentWord  = regexp.MustCompile(`(?i)\bagents?\b|\bby hand\b|\bsession\b`)
	markup     = regexp.MustCompile("[`*<>{}\\[\\]|#]|(^|\\s)_|_(\\s|$)")
)

// Plain says whether text is plain words the operator reads at a glance, and if not, what is not: an
// identifier (a hash, a numbered id, a dotted name such as a key or a verb), a Go duration, a clock time
// or date (the channel says when, in the operator's time), a command's flag, markup, a line break, or
// anything the operator's channel withholds (ADR 0234 §6). machines are names that may appear.
func Plain(text string, machines ...string) (string, bool) {
	if strings.TrimSpace(text) == "" {
		return "nothing is said", false
	}
	if strings.ContainsAny(text, "\n\r\t") {
		return "a line break", false
	}
	if m := markup.FindString(text); m != "" {
		return "markup (" + m + ")", false
	}
	for _, shape := range []struct {
		re   *regexp.Regexp
		what string
	}{{hexID, "a hash"}, {numberedID, "a numbered id"}, {dotted, "a dotted name"}, {goDuration, "a duration in code"},
		{clockTime, "a clock time or date"}, {flag, "a command's flag"}} {
		if m := shape.re.FindString(text); m != "" {
			if shape.re == hexID && !strings.ContainsAny(m, "0123456789") {
				continue // a word of letters a to f only
			}
			return shape.what + " (" + strings.TrimSpace(m) + ")", false
		}
	}
	if r, ok := outward.Check(text, machines...); !ok {
		return r.String(), false
	}
	return "", true
}

// PlainWords checks all three, with their bounds.
func PlainWords(w Words, machines ...string) (string, bool) {
	if why, ok := Plain(w.Headline, machines...); !ok {
		return "headline: " + why, false
	}
	if len(w.Headline) > HeadlineMax {
		return fmt.Sprintf("headline: longer than %d characters", HeadlineMax), false
	}
	if why, ok := Plain(w.Explanation, machines...); !ok {
		return "explanation: " + why, false
	}
	if len(w.Explanation) > ExplanationMax {
		return fmt.Sprintf("explanation: longer than %d characters", ExplanationMax), false
	}
	for _, m := range agentWord.FindAllString(w.Explanation, -1) {
		if !strings.EqualFold(m, "by hand") { // "repaired by hand" is a fact; telling to act by hand is not
			return "explanation: sends the operator elsewhere (" + m + ")", false
		}
	}
	if w.Needs != "" {
		if why, ok := Plain(w.Needs, machines...); !ok {
			return "needs: " + why, false
		}
		if m := agentWord.FindString(w.Needs); m != "" {
			return "needs: not something the operator does themselves (" + m + ")", false
		}
		if len(w.Needs) > NeedsMax || !strings.HasSuffix(w.Needs, ".") {
			return fmt.Sprintf("needs: one sentence of at most %d characters, ending in a full stop", NeedsMax), false
		}
	}
	for _, a := range w.Actions {
		if a.Label == "" || len(a.Label) > 24 || a.Verb == "" {
			return fmt.Sprintf("action %q: a short label and a verb", a.Label), false
		}
	}
	if why, ok := Plain(w.Resolved, machines...); !ok {
		return "resolved: " + why, false
	}
	if len(w.Resolved) > HeadlineMax+20 {
		return fmt.Sprintf("resolved: longer than %d characters", HeadlineMax+20), false
	}
	return "", true
}

// plainly gives an observation its plain words: its own, its kind's, or its scope's.
func plainly(o Observation) Observation {
	machines := append([]string{o.Machine}, o.Also...)
	given := Words{Headline: o.Headline, Explanation: o.Explanation, Resolved: o.Resolved, Needs: o.Needs,
		Actions: o.Actions}
	var w Words
	from := ""
	switch {
	case given.Headline != "":
		w, from = given, "its source"
	default:
		wordingsMu.RLock()
		fn := wordings[o.Kind]
		wordingsMu.RUnlock()
		if fn != nil {
			w, from = fn(o), "the wording of "+o.Kind
			if given.Explanation != "" {
				w.Explanation = given.Explanation
			}
			if given.Resolved != "" {
				w.Resolved = given.Resolved
			}
			if given.Needs != "" {
				w.Needs = given.Needs
			}
			if len(given.Actions) > 0 {
				w.Actions = given.Actions
			}
		}
	}
	if w.Headline != "" && w.Resolved == "" {
		w.Resolved = "Resolved: " + lowerFirst(w.Headline)
	}
	if from == "" {
		if Unworded != nil {
			Unworded(o, "the kind "+o.Kind+" has no plain words")
		}
		w = scopeWords(o)
	} else if why, ok := PlainWords(w, machines...); !ok {
		if Unworded != nil {
			Unworded(o, from+" is not plain: "+why)
		}
		w = scopeWords(o)
	}
	o.Headline, o.Resolved, o.Needs, o.Actions = w.Headline, w.Resolved, w.Needs, w.Actions
	o.Explanation = Verdict(w.Needs, w.Explanation)
	return o
}

// Verdict is an explanation opened by its verdict.
func Verdict(needs, explanation string) string {
	if needs == "" {
		return strings.TrimSpace(NothingToDo + " " + explanation)
	}
	return strings.TrimSpace(NeedsYou + " " + needs + " " + explanation)
}

// Escalated is what a condition needs once a healer gave up on it, where its words needed nothing.
const Escalated = "the mesh tried to repair this and could not; read the details to decide what to do."

// escalatedWords turns "Nothing for you to do." into "Needs you:" once a healer gave up.
func escalatedWords(c *Condition) {
	if c.Escalated() && c.Needs == "" {
		c.Needs = Escalated
		c.Explanation = Verdict(c.Needs, strings.TrimSpace(strings.TrimPrefix(c.Explanation, NothingToDo)))
	}
}

// scopeWords is what is said of a kind with no words of its own: what kind of thing, and which one
// where its name is a name (a machine, a module), never an id.
func scopeWords(o Observation) Words {
	thing := ThingWords(o)
	what := strings.ReplaceAll(o.Kind, "-", " ")
	w := Words{
		Headline:    Capital(thing) + " needs a look",
		Explanation: fmt.Sprintf("The mesh noticed a problem it calls %q with %s.", what, thing),
		Resolved:    "Resolved: " + thing + " is fine again",
		Needs:       ResolverNeeds(o),
	}
	if _, ok := PlainWords(w, append([]string{o.Machine}, o.Also...)...); !ok {
		w = Words{Headline: "Something in the mesh needs a look",
			Explanation: "The mesh noticed a problem it has no plain words for yet.",
			Resolved:    "Resolved: the mesh is fine again", Needs: ResolverNeeds(o)}
	}
	return w
}

// ThingWords is what a condition is about, in plain words: "the machine ace", "openrazer on g14", "a
// delivery". An id that is not a name (a plan's, a delivery's, a call's) is never said.
func ThingWords(o Observation) string {
	switch o.Scope {
	case ScopeMachine:
		if o.Machine != "" {
			return o.Machine
		}
		return "a machine"
	case ScopeModule:
		module := strings.TrimSuffix(o.ID, "."+o.Machine)
		if o.Machine != "" && module != "" && !strings.Contains(module, ".") {
			return module + " on " + o.Machine
		}
		return "a module"
	case ScopeProvider:
		if module, _, _ := strings.Cut(o.ID, "."); module != "" && o.Machine != "" {
			return module + " on " + o.Machine
		}
		return "a provider"
	case ScopePlan:
		return "a walk"
	case ScopeDelivery:
		return "a delivery"
	case ScopeBuild:
		return "a build"
	case ScopeCall:
		return "a tool call"
	case ScopeMerge:
		return "a merge"
	case ScopeSeat:
		return "a seat's holder"
	case ScopeBus:
		return "the bus"
	case ScopeCore:
		return "the controller"
	case ScopeProbe:
		return "the self-check"
	}
	return "the mesh"
}

// ResolverNeeds is what the operator needs to do, from who resolves it: nothing, unless only a person can.
func ResolverNeeds(o Observation) string {
	if o.Resolver == ResolverOperator {
		return "the mesh does not repair this by itself; read the details to decide what to do."
	}
	return ""
}

// Capital is s with its first letter upper case.
func Capital(s string) string {
	if s == "" {
		return s
	}
	return strings.ToUpper(s[:1]) + s[1:]
}

func lowerFirst(s string) string {
	if s == "" || (len(s) > 1 && strings.ToUpper(s[:2]) == s[:2]) {
		return s
	}
	return strings.ToLower(s[:1]) + s[1:]
}