package build

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

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

// **The tool builder_seat_queue reads a build seat's stream as the builder reads it** (novox/hq issue 1945 note 62; the
// instruction "tools are how a module is spoken to"): the messages waiting on SEAT_NODE_BUILD_<LANGUAGE>, bounded, each
// with its ask, its age, the state of the step a build node wrote for it, and whether the builder counts it as still
// waiting (AskSeen.Waits) or as given up on. Only the builder's own account may read the stream (issue 1910): the tools
// bundle writes the read into the builder's state queues, keyed by the language, which the builder watches and answers
// there, as builder_ask_again does through reasks.
const (
	SeatQueueTool = "builder_seat_queue"
	// QueuesState is the builder's state of queue reads: the bucket mesh-delivery-builder_queues, keyed by the language.
	QueuesState  = "queues"
	QueuesBucket = delivery.BuilderModule + "_" + QueuesState
	// DefaultQueueLimit and MaxQueueLimit bound the messages read of each kind.
	DefaultQueueLimit = 50
	MaxQueueLimit     = 500
)

// QueueNote says what the read cannot show.
const QueueNote = "the builder may not read the seat workers' delivery counts or ack floors ($JS.API.CONSUMER.INFO.<stream>.<worker> is " +
	"granted to the delivery view alone): a message counts as given up on when no node wrote its step and a node took an ask of its kind " +
	"asked after it; nats.nats_streams shows the workers' pending and waiting pulls"

// QueueAsk is a value of the queues state: a read asked (limit, who, when) and, once the builder read the stream, its answer.
type QueueAsk struct {
	V        int        `json:"v"`
	Limit    int        `json:"limit"`
	By       string     `json:"by,omitempty"`
	At       time.Time  `json:"at"`
	Answered time.Time  `json:"answered,omitzero"`
	Error    string     `json:"error,omitempty"`
	Queue    *SeatQueue `json:"queue,omitempty"`
}

// SeatQueue is what the builder read of one build seat's stream.
type SeatQueue struct {
	Language string      `json:"language"`
	Stream   string      `json:"stream"`
	Messages uint64      `json:"messages"`
	FirstSeq uint64      `json:"first_seq"`
	LastSeq  uint64      `json:"last_seq"`
	Kinds    []KindQueue `json:"kinds"`
	Note     string      `json:"note"`
}

// KindQueue is one kind's messages on the stream, oldest first: how many the builder counts as waiting, the ask asked
// last a build node took of the kind (or of one pulled after it), and each message.
type KindQueue struct {
	Kind     string        `json:"kind"`
	Read     int           `json:"read"`
	Waiting  int           `json:"waiting"`
	GivenUp  int           `json:"given_up_or_taken"`
	Last     *Taken        `json:"last_taken,omitempty"`
	Messages []QueuedState `json:"messages"`
}

// QueuedState is one message as the tool shows it.
type QueuedState struct {
	Queued
	AgeSeconds int64 `json:"age_s"`
	Waits      bool  `json:"waits"`
}

// NewKindQueue is seen's messages ahead as one kind's queue at now.
func NewKindQueue(kind string, seen AskSeen, now time.Time) KindQueue {
	k := KindQueue{Kind: kind, Read: len(seen.Ahead), Last: seen.Last}
	for _, q := range seen.Ahead {
		w := seen.Waits(q)
		if w {
			k.Waiting++
		} else {
			k.GivenUp++
		}
		k.Messages = append(k.Messages, QueuedState{Queued: q, AgeSeconds: int64(now.Sub(q.PutAt) / time.Second), Waits: w})
	}
	return k
}

// NewQueueAsk is the value builder_seat_queue writes for a language: its key and the value.
func NewQueueAsk(language string, limit int, by string, at time.Time) (string, []byte, error) {
	if _, err := delivery.AskStream(language); err != nil {
		return "", nil, fmt.Errorf("language: %w", err)
	}
	if limit <= 0 {
		limit = DefaultQueueLimit
	}
	data, err := json.Marshal(QueueAsk{V: 1, Limit: min(limit, MaxQueueLimit), By: by, At: at.UTC()})
	return language, data, err
}

// DecodeQueueAsk reads a queues value.
func DecodeQueueAsk(data []byte) (QueueAsk, error) {
	var a QueueAsk
	if err := json.Unmarshal(data, &a); err != nil {
		return a, err
	}
	if a.V != 1 {
		return a, fmt.Errorf("a queues value of version %d, not 1", a.V)
	}
	return a, nil
}

// LanguageOf is the language a tool's seat or language argument names: go, node or image, or node-build-<language>.
func LanguageOf(arg string) string {
	return strings.TrimPrefix(strings.TrimSpace(arg), "node-build-")
}