package assign

import (
	"fmt"
	"time"

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

// A put (novox/hq ADR 0546): one version of a module put on one node by the assigner's tool assigner_put. The tool writes the put
// key; each pass takes it one step further from what the world holds (StepPut), and the rules pass over the node's want for
// the module from its asking until it ends (Module.Puts).

// ComposeWithin is how long a put waits for the composition and grant it needs (a take-in of a build just done writes them)
// before it is refused.
const ComposeWithin = 10 * time.Minute

// PutWorld is what one step of a put reads.
type PutWorld struct {
	Node, Module string
	Put          delivery.Put
	// Assigned says the module stands assigned to the node.
	Assigned bool
	// Bus says the module provides the mesh's bus (ADR 0539 §15); Recorded that it is of policy record (§14).
	Bus, Recorded bool
	// Build is the state of the builder's build at the put's fingerprint, "" when no key is written; BuildWords its error.
	Build, BuildWords string
	// Newest is the module's newest fingerprint at the trunk, which the builder builds by itself.
	Newest string
	// Composed is the composition of the module for the node at the fingerprint, as its writer holds it; nil when there is
	// none. Granted says the grant at the fingerprint names the node's accounts. Both are read, never asked for (clause 4).
	Composed *delivery.ComposedDigest
	Granted  bool
	// Answer is the option the operator chose on this put's own ask (its asking, PutAsking), "" when none; AskExpired says
	// that ask expired unanswered.
	Answer     string
	AskExpired bool
	// Snapshot says where the bus's streams were snapshotted for this put, once they were; Snapshotting that it was
	// asked; SnapshotFailed why it was not taken.
	Snapshot       string
	Snapshotting   bool
	SnapshotFailed string
	// Have is what the node says it runs of the module; nil when it says nothing.
	Have *delivery.Have
	Now  time.Time
}

// PutNext is what a step decides: the put as it stands after it, and the acts the pass does for it.
type PutNext struct {
	Put delivery.Put
	// Ask writes the put's ask about the move (PutAsk).
	Ask bool
	// Snapshot has the bus's node back the bus up now, its dump the streams' snapshot (ADR 0235).
	Snapshot bool
	// Warranted records, once, in the controller's hand-act log that the bus's want was written on the operator's warrant.
	Warranted bool
}

// StepPut takes a put one step further from what the world holds (ADR 0546 clauses 3 to 8).
func StepPut(w PutWorld) PutNext {
	p := w.Put
	if delivery.PutEnded(p.Step) {
		return PutNext{Put: p}
	}
	say := func(step, format string, args ...any) PutNext {
		return PutNext{Put: p.Said(w.Now, step, fmt.Sprintf(format, args...))}
	}
	fp := short(p.FP)
	if !w.Assigned {
		return say(delivery.PutRefused, "%s is not assigned to %s: a put moves a module where it stands assigned (propose its placement first)", w.Module, w.Node)
	}
	switch w.Build {
	case delivery.BuildDone:
	case delivery.BuildFailed:
		return say(delivery.PutRefused, "the builder's build of %s at %s failed: %s", w.Module, fp, w.BuildWords)
	case "":
		if p.FP != w.Newest {
			// The builder builds the trunk's newest fingerprint and the candidates', and takes no ask for another yet (ADR 0546
			// clause 3): an older fingerprint it never built, or whose key it removed, cannot be put.
			return say(delivery.PutRefused, "the builder holds no build of %s at %s, and builds by itself only the trunk's newest (%s): put that, or a version it built", w.Module, fp, short(w.Newest))
		}
		return say(delivery.PutBuild, "waits for the builder's build of %s at %s, the trunk's newest, which it builds by itself", w.Module, fp)
	default:
		return say(delivery.PutBuild, "waits for the builder's build of %s at %s, which is %s", w.Module, fp, w.Build)
	}
	if w.Composed == nil || !w.Granted {
		missing := fmt.Sprintf("no composition of %s for %s at %s is written", w.Module, w.Node, fp)
		if w.Composed != nil {
			missing = fmt.Sprintf("the grant of %s at %s does not name %s's accounts", w.Module, fp, w.Node)
		}
		since := w.Now
		if p.Step == delivery.PutCompose && len(p.Steps) > 0 {
			since = p.Steps[len(p.Steps)-1].At
		}
		if w.Now.Sub(since) > ComposeWithin {
			return say(delivery.PutRefused, "%s after %s: only a composition written by the take-in of its build (or one of the five kept) is put; "+
				"for another the hand path is mesh-hand-compose (ADR 0539 §10)", missing, ComposeWithin)
		}
		return say(delivery.PutCompose, "waits up to %s: %s yet", ComposeWithin, missing)
	}
	d := *w.Composed
	if p.Step == delivery.PutWanted || p.Step == delivery.PutHolding {
		return PutNext{Put: applied(w, p)}
	}
	p.Composed = d.Digest
	if needsPerson(w, d) {
		switch w.Answer {
		case OptionNo:
			return say(delivery.PutRefused, "the operator answered no to putting %s at %s on %s", w.Module, fp, w.Node)
		case OptionYes:
		default:
			if w.AskExpired {
				return say(delivery.PutRefused, "the operator's ask about putting %s at %s on %s expired unanswered: the node keeps what it runs", w.Module, fp, w.Node)
			}
			next := say(delivery.PutPerson, "waits for the operator's yes to putting %s at %s on %s (composition %s, judged %s)", w.Module, fp, w.Node, short(d.Digest), d.Judgement)
			if p.Ask == "" {
				next.Ask = true
				next.Put.Ask, _ = delivery.RecordAskKey(w.Node, w.Module, d.Digest)
			}
			return next
		}
		if w.Bus {
			switch {
			case w.Snapshot != "":
				p.Snapshot = w.Snapshot
			case w.SnapshotFailed != "":
				return say(delivery.PutRefused, "the bus's streams were not snapshotted, so the bus is not put: %s", w.SnapshotFailed)
			case w.Snapshotting:
				return say(delivery.PutSnapshot, "the operator said yes; waits for %s's backup holder to snapshot the bus's streams", w.Node)
			default:
				next := say(delivery.PutSnapshot, "the operator said yes; asked %s's backup holder to snapshot the bus's streams", w.Node)
				next.Snapshot = true
				return next
			}
		}
	}
	words := fmt.Sprintf("the want of %s on %s names %s (composition %s)", w.Module, w.Node, fp, short(d.Digest))
	if p.Hold {
		words += ", held until released"
	}
	if p.Snapshot != "" {
		words += "; the streams were snapshotted: " + p.Snapshot
	}
	next := PutNext{Put: applied(w, p.Said(w.Now, delivery.PutWanted, words))}
	next.Warranted = w.Bus && p.Ask != ""
	return next
}

// applied is a wanted put once the node's have says how it went: holding or done when it runs the composition healthy.
func applied(w PutWorld, p delivery.Put) delivery.Put {
	h := w.Have
	if h == nil || h.FP != p.FP || h.Composed != p.Composed {
		return p
	}
	switch {
	case h.Phase == delivery.PhaseRunning && h.Health == delivery.HealthOK && p.Hold:
		return p.Said(w.Now, delivery.PutHolding, fmt.Sprintf("%s runs %s at %s healthy; held there until released", w.Node, w.Module, short(p.FP)))
	case h.Phase == delivery.PhaseRunning && h.Health == delivery.HealthOK:
		return p.Said(w.Now, delivery.PutDone, fmt.Sprintf("%s runs %s at %s healthy; the rules write its want again", w.Node, w.Module, short(p.FP)))
	case failed(*h):
		return p.Said(w.Now, p.Step, fmt.Sprintf("%s runs %s at %s and its health check failed: %s", w.Node, w.Module, short(p.FP), h.Detail))
	}
	return p
}

// needsPerson says whether the put's move waits for the operator: any move of the bus but a revision at the fingerprint the
// node runs that changes only its user list (ADR 0539 §7, §15), and a move of a module of policy record judged to recreate a
// container, move data, or that cannot be judged (§14).
func needsPerson(w PutWorld, d delivery.ComposedDigest) bool {
	runs := w.Have != nil && w.Have.FP == w.Put.FP
	if runs && w.Have.Composed == d.Digest {
		return false // the node runs this composition already: nothing moves
	}
	if w.Bus {
		return !(runs && d.UserListOnly)
	}
	if !w.Recorded {
		return false
	}
	return d.Judgement == delivery.JudgedRecreates || d.Judgement == delivery.JudgedMovesData || d.Judgement == delivery.JudgedCannot
}

// PutWant is the want a put writes once it is wanted: the fingerprint and composition, marked put, and held when it holds.
func PutWant(p delivery.Put) delivery.Want {
	return delivery.Want{FP: p.FP, Composed: p.Composed, Put: true, Hold: p.Hold, Words: "put: " + p.Why}
}

// PutOwns says what a put does to the node's want: owns says the rules pass over it, want the want it writes (nil: what
// stands stays). A put owns the want from its asking until it ends; a held put ends only when released.
func PutOwns(p delivery.Put) (want *delivery.Want, owns bool) {
	switch p.Step {
	case delivery.PutWanted, delivery.PutHolding:
		w := PutWant(p)
		return &w, true
	case delivery.PutDone, delivery.PutReleased, delivery.PutRefused:
		return nil, false
	}
	return nil, true
}

// PutAsking is a put's own asking number: when it was asked, in milliseconds. Each put asked under the same key is another
// asking, so the ask is written again under an id of its own and an answer to an earlier put, whose warrant names that put's
// asking, never counts for a later one (ADR 0546 clause 8: one approval binds one act).
func PutAsking(p delivery.Put) int {
	if n := p.At.UnixMilli(); n > 0 {
		return int(n)
	}
	return 0
}

// PutAct is the act a bus put's yes binds and that is performed when its want is written.
func PutAct(node, module, fp, composed string) asks.Act {
	return asks.Act{"put": "want", "node": node, "module": module, "fp": fp, "composed": composed}
}

// PutAsk is the ask about a put's move (ADR 0546 clauses 7 and 8), under the record ask's key of the composition so the
// teller relays it and its answer as any record ask's. For the bus its yes is of level approve and binds the act, so only a
// channel that proves who answered takes it (ADR 0259), never the view.
func PutAsk(key, node, module string, p delivery.Put, d delivery.ComposedDigest, bus bool, now time.Time) (delivery.AssignerAsk, error) {
	yes := asks.Option{ID: OptionYes, Label: "Yes, put it", Does: "the node is told to apply " + module + " at " + short(p.FP), Level: asks.Acknowledge}
	what := map[delivery.Judgement]string{
		delivery.JudgedRecreates: "recreates a container",
		delivery.JudgedMovesData: "moves the module's data",
		delivery.JudgedCannot:    "cannot be judged: " + d.Words,
		delivery.JudgedNeither:   "recreates no container and moves no data",
		delivery.JudgedUnchanged: "changes nothing the node runs",
	}[d.Judgement]
	explanation := fmt.Sprintf("Asked to put %s at version %s on %s: %s. The move %s.", module, short(p.FP), node, p.Why, what)
	expires := now.Add(7 * 24 * time.Hour)
	if bus {
		binds, err := asks.ActDigest(PutAct(node, module, p.FP, d.Digest))
		if err != nil {
			return delivery.AssignerAsk{}, err
		}
		yes.Level, yes.Binds = asks.Approve, binds
		yes.Does = "the bus's streams are snapshotted, then " + node + " is told to apply the bus at " + short(p.FP)
		explanation += " It is the mesh's bus: every module reconnects while it restarts, and its streams are snapshotted first."
		expires = now.Add(asks.ApproveLasts)
	}
	return delivery.AssignerAsk{Ask: asks.Ask{
		ID:          delivery.AskingID(key, PutAsking(p)),
		Headline:    fmt.Sprintf("Put %s on %s?", module, node),
		Explanation: explanation,
		Options: []asks.Option{yes,
			{ID: OptionNo, Label: "No", Does: "the node keeps what it runs, and the put is refused", Level: asks.Acknowledge}},
		Who:      asks.Operator,
		Expires:  expires,
		OnExpiry: "the node keeps what it runs",
		About:    key,
	}, Asking: PutAsking(p)}, nil
}