package versions

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

	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/builds"
	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/builds/forms"
	"git.novox.be/novox/mesh-delivery/sdk/window"
)

// The old reference form's window (design 51 *Every build keeps the old reference form*, ADR 0624 §1, ADR 0618 §2-§4,
// DLV-B9). Which forms a build key keeps is mesh-delivery's sdk/forms (Kept, Choose), the counted nodes' statements the
// builder's state engine-reads; this is only the window over them: open while a counted node-engine, present or away,
// reads of some artifact kind none of the newest form the builder knows for it, so an older form stays in new build keys
// for it; closed, said once with `old-form-closed` and a log line, when none does. It moves on what moves a statement
// (the node-engine seat's verb `manifest-reads` and its event `manifest-reads-changed`), the assignments, a hand drop and
// each build key written; never on a timer.

// OldFormState is the builder's state of the window: one key, OldFormKey, an OldFormWindow. builder_old_form reads it.
const (
	OldFormState = "old-form"
	OldFormKey   = "window"
)

// OldFormBucket is that state's bucket.
const OldFormBucket = builds.BuilderModule + "_" + OldFormState

// OldFormHeld is the finding of a node holding the window open for FindingAfter, about that node, cleared when the
// window closes or the node no longer holds it.
const OldFormHeld = "old-form-held"

// Holding are the counted nodes, those dropped by hand left out, whose engine reads, of some artifact kind fs knows, not
// the newest form of that kind: the nodes for which an older form stays in new build keys (forms.ArtifactForms.Kept). A
// node stating nothing reads the first forms (fs.Reads), sorted.
func Holding(fs forms.ArtifactForms, counted map[string][]string, dropped map[string]bool) []string {
	newest := map[string]string{} // kind -> newest form
	var kinds []string
	for _, f := range fs {
		for _, k := range f.Kinds {
			if _, ok := newest[k]; !ok {
				kinds = append(kinds, k)
			}
			newest[k] = f.Name
		}
	}
	var out []string
	for node, stated := range counted {
		if dropped[node] {
			continue
		}
		for _, k := range kinds {
			if !fs.Reads(stated, newest[k]) {
				out = append(out, node)
				break
			}
		}
	}
	sort.Strings(out)
	return out
}

// OldFormWindow is the window's record: whether it is open, who holds it and since when (window.WindowHeld, the part
// every window keeper shares), and the nodes dropped by hand; what builder_old_form answers and what `old-form-closed`
// carries when it closes.
type OldFormWindow struct {
	window.WindowHeld
	Dropped []Dropped `json:"dropped,omitempty"`
}

// Dropped is one retired node dropped from the count by hand (builder_old_form): a hand act with who and why.
type Dropped struct {
	Node string    `json:"node"`
	By   string    `json:"by"`
	Why  string    `json:"why"`
	At   time.Time `json:"at"`
}

// OldFormClosedBody is the body of OldFormClosedEvent (design 51): when, the nodes that held it last and the nodes dropped
// by hand.
type OldFormClosedBody struct {
	At          time.Time `json:"at"`
	LastHolding []string  `json:"last_holding,omitempty"`
	Dropped     []Dropped `json:"dropped,omitempty"`
}

// FindingAfter is how long a node holds the window open before it is the builder's finding naming the node.
const FindingAfter = 7 * 24 * time.Hour

// Step moves the window by mesh-sdk's one window rule (window.StepWindow): named is every counted node the read named,
// those dropped by hand included, and holding those of them holding the window (Holding). A read naming no node (no
// assignments read yet, an empty node_haves) judges nothing, so it never closes the window. It answers the new window,
// whether it closed in this step (so the builder says `old-form-closed` and its log line once), and the nodes holding it
// past FindingAfter (the finding, cleared for every other node).
func (w OldFormWindow) Step(named, holding []string, now time.Time) (next OldFormWindow, closed bool, overdue []string) {
	held, closed, overdue := window.StepWindow(w.WindowHeld, named, holding, now, FindingAfter)
	return OldFormWindow{WindowHeld: held, Dropped: w.Dropped}, closed, overdue
}

// Drop drops a retired node from the count by hand; dropping it again changes nothing.
func (w OldFormWindow) Drop(node, by, why string, at time.Time) (OldFormWindow, error) {
	node, why = strings.TrimSpace(node), strings.TrimSpace(why)
	if node == "" || why == "" {
		return w, errors.New("name the retired node (node) and say why it leaves the count (why)")
	}
	if w.DroppedSet()[node] {
		return w, nil
	}
	w.Dropped = append(slices.Clone(w.Dropped), Dropped{Node: node, By: by, Why: why, At: at.UTC()})
	return w, nil
}

// DroppedSet is the dropped nodes, as Holding takes them.
func (w OldFormWindow) DroppedSet() map[string]bool {
	out := map[string]bool{}
	for _, d := range w.Dropped {
		out[d.Node] = true
	}
	return out
}

// Closing is the event's body of a window that closed in a Step.
func (w OldFormWindow) Closing() OldFormClosedBody {
	return OldFormClosedBody{At: w.Closed, LastHolding: w.LastHolding, Dropped: w.Dropped}
}

// DecodeOldFormWindow reads the state's value; none is a closed window no node holds.
func DecodeOldFormWindow(raw []byte) (OldFormWindow, error) {
	var w OldFormWindow
	if len(raw) == 0 {
		return w, nil
	}
	if err := json.Unmarshal(raw, &w); err != nil {
		return OldFormWindow{}, fmt.Errorf("the old-form window is not readable: %w", err)
	}
	return w, nil
}

// OldFormDescription is builder_old_form's description.
const OldFormDescription = "The old reference form's window (design 51 *Every build keeps the old reference form*, ADR 0624): whether it is open, " +
	"the counted nodes, present or away, whose node-engine reads an older reference form alone and since when (a node holding it seven days " +
	"is the builder's finding " + OldFormHeld + "), when it last closed and who held it then, and the retired nodes dropped from the count by " +
	"hand. With drop (a node) and why, drops that retired node from the count by hand, a hand act the builder answers; a node still placed " +
	"leaves the count by itself only when the assignments no longer names it. builder_engine_reads shows what each node's engine states."

// AnswerOldForm is builder_old_form's read: the window as the state holds it.
func AnswerOldForm(r Reader) (OldFormWindow, error) {
	raw, ok, err := r.Get(OldFormKey)
	if err != nil || !ok {
		return OldFormWindow{}, err
	}
	return DecodeOldFormWindow(raw)
}