package view

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

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

// `status` is the view's derivation (novox/hq ADR 0564 §10, Limits 7, issue 1952 V1): what is wrong, quiet and on its way,
// read from the buckets it watches, never from a summary someone writes (research 072 §2), so the controller's status, its
// summary and the probe D9 go with its lease. Each part comes from one bucket:
//   - Conditions: the condition keeper's open conditions (mesh-conditions.conditions), urgent first, then oldest;
//   - Quiet: the watchman's presence of each node that is offline, and its stuck keys not moved;
//   - Moving: each module whose want and have differ, as mesh-sdk's delivery.MotionOf derives it (moving or stuck);
//   - Heals: what mesh-healers did in the last seven days (mesh-healers.attempts), by outcome.
// A bucket that cannot be read says so in its part's Unread, never as none.

// StatusTool is the view's tool that answers status.
const StatusTool = "view_status"

// The states status reads, as the view's manifest names them.
const (
	StatusConditionsState = health.KeeperModule + "." + health.ConditionsState
	StatusAttemptsState   = health.HealersModule + "." + health.AttemptsState
	StatusPresenceState   = delivery.WatchmanModule + ".presence"
	StatusStuckState      = delivery.WatchmanModule + ".stuck"
)

// HealsWithin is how far back status counts the healers' acts.
const HealsWithin = 7 * 24 * time.Hour

// StatusRead is the five buckets status reads, as a tool reads them.
type StatusRead struct {
	Conditions, Attempts, Presence, Stuck, Wants, Haves StateRead
}

// Status is the view's answer to status.
type Status struct {
	Conditions       []StatusCondition `json:"conditions"`
	ConditionsUnread string            `json:"conditions-unread,omitempty"`
	Quiet            []StatusQuiet     `json:"quiet"`
	QuietUnread      string            `json:"quiet-unread,omitempty"`
	Moving           []StatusMoving    `json:"moving"`
	MovingUnread     string            `json:"moving-unread,omitempty"`
	Heals            map[string]int    `json:"heals-this-week"`
	HealsUnread      string            `json:"heals-unread,omitempty"`
	// Well says nothing is open, quiet or stuck; a part unread is not well.
	Well bool `json:"well"`
}

// StatusCondition is one open condition in brief.
type StatusCondition struct {
	Key      string    `json:"key"`
	Severity string    `json:"severity"`
	Machine  string    `json:"machine,omitempty"`
	Summary  string    `json:"summary"`
	Raised   time.Time `json:"raised"`
	Silenced bool      `json:"silenced,omitempty"`
}

// StatusQuiet is a node offline, or a key the watchman says stopped moving.
type StatusQuiet struct {
	Key   string    `json:"key"`
	What  string    `json:"what"`
	Since time.Time `json:"since,omitzero"`
}

// StatusMoving is a module whose want and have differ on a node.
type StatusMoving struct {
	Node    string `json:"node"`
	Module  string `json:"module"`
	State   string `json:"state"`
	Outcome string `json:"outcome,omitempty"`
	Words   string `json:"words,omitempty"`
	FromFP  string `json:"from_fp,omitempty"`
	ToFP    string `json:"to_fp"`
}

func values(s StateRead) (map[string]json.RawMessage, error) {
	if s.Keys == nil || s.Get == nil {
		return nil, fmt.Errorf("not read here")
	}
	keys, err := s.Keys()
	if err != nil {
		return nil, err
	}
	out := map[string]json.RawMessage{}
	for _, k := range keys {
		v, err := s.Get(k)
		if err != nil {
			return nil, fmt.Errorf("%s: %w", k, err)
		}
		if v != nil {
			out[k] = v
		}
	}
	return out, nil
}

// DeriveStatus is status from the buckets r reads, at now.
func DeriveStatus(r StatusRead, now time.Time) Status {
	st := Status{Conditions: []StatusCondition{}, Quiet: []StatusQuiet{}, Moving: []StatusMoving{}, Heals: map[string]int{}}

	if raw, err := values(r.Conditions); err != nil {
		st.ConditionsUnread = "the condition keeper's conditions cannot be read: " + err.Error()
	} else {
		var open []health.Condition
		for _, v := range raw {
			var c health.Condition
			if json.Unmarshal(v, &c) == nil && c.Key != "" {
				open = append(open, c)
			}
		}
		health.Order(open)
		for _, c := range open {
			st.Conditions = append(st.Conditions, StatusCondition{Key: c.Key, Severity: string(c.Severity), Machine: c.Subject.Machine,
				Summary: c.Summary, Raised: c.Raised, Silenced: c.SilencedAt(now)})
		}
	}

	presence, perr := values(r.Presence)
	stuck, serr := values(r.Stuck)
	switch {
	case perr != nil:
		st.QuietUnread = "the watchman's presence cannot be read: " + perr.Error()
	case serr != nil:
		st.QuietUnread = "the watchman's stuck keys cannot be read: " + serr.Error()
	default:
		for k, v := range presence {
			if p, err := delivery.DecodePresence(v); err == nil && !p.Online {
				st.Quiet = append(st.Quiet, StatusQuiet{Key: k, What: "offline"})
			}
		}
		for k, v := range stuck {
			if s, err := delivery.DecodeStuck(v); err == nil && !s.Moved {
				st.Quiet = append(st.Quiet, StatusQuiet{Key: k, What: "stopped moving: it waited for " + s.Waited, Since: s.Since})
			}
		}
		sort.Slice(st.Quiet, func(i, j int) bool { return st.Quiet[i].Key < st.Quiet[j].Key })
	}

	wants, werr := values(r.Wants)
	haves, herr := values(r.Haves)
	switch {
	case werr != nil:
		st.MovingUnread = "the assigner's wants cannot be read: " + werr.Error()
	case herr != nil:
		st.MovingUnread = "the nodes' haves cannot be read: " + herr.Error()
	default:
		for wk, v := range wants {
			node, module, err := delivery.ParseWantKey(wk)
			if err != nil {
				continue
			}
			w, err := delivery.DecodeWant(v)
			if err != nil {
				continue
			}
			hk, _ := delivery.HaveKey(node, module)
			var h delivery.Have
			hv, has := haves[hk]
			if has {
				if h, err = delivery.DecodeHave(hv); err != nil {
					has = false
				}
			}
			words, stopped := "", false
			if sk, err := delivery.StuckKey(delivery.AssignerWantsBucket, wk); err == nil && serr == nil {
				if s, err := delivery.DecodeStuck(stuck[sk]); err == nil && !s.Moved {
					words, stopped = s.Waited, true
				}
			}
			m := delivery.MotionOf(w, true, h, has, words, stopped)
			if m.State == "" || m.State == delivery.MotionSettled {
				continue
			}
			row := StatusMoving{Node: node, Module: module, State: m.State, Outcome: m.Outcome, Words: m.Words, ToFP: w.FP}
			if has {
				row.FromFP = h.FP
			}
			st.Moving = append(st.Moving, row)
		}
		sort.Slice(st.Moving, func(i, j int) bool {
			if st.Moving[i].Node != st.Moving[j].Node {
				return st.Moving[i].Node < st.Moving[j].Node
			}
			return st.Moving[i].Module < st.Moving[j].Module
		})
	}

	if raw, err := values(r.Attempts); err != nil {
		st.HealsUnread = "mesh-healers' attempts cannot be read: " + err.Error()
	} else {
		for _, v := range raw {
			var a health.Attempt
			if json.Unmarshal(v, &a) != nil || now.Sub(a.Begun) > HealsWithin {
				continue
			}
			outcome := a.Outcome
			if outcome == "" {
				outcome = health.OutcomeActing
			}
			st.Heals[outcome]++
		}
	}

	stuckMoving := false
	for _, m := range st.Moving {
		stuckMoving = stuckMoving || m.State == delivery.MotionStuck
	}
	st.Well = len(st.Conditions) == 0 && len(st.Quiet) == 0 && !stuckMoving &&
		st.ConditionsUnread == "" && st.QuietUnread == "" && st.MovingUnread == ""
	return st
}