package grants

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

	"git.novox.be/novox/mesh-sdk/go/health"
	"mesh-grants/internal/buscompose"
)

// CallRootFree is the node seat's verb that judges one machine root-free (novox/hq ADR 0259 §8, ADR 0563 §6), asked of
// that machine's own engine as `seat:node-engine.root-free@<machine>`: the judgement the composer needs and the part
// cannot make from the bus (issue 1945). Only that machine's engine answers it, and the controller takes no part in it
// (ADR 0571 §11, issue 1955). The messenger asks the same verb the same way.
const CallRootFree = "seat:node-engine.root-free"

// The condition events the part hears (never a timer): a machine's root-free word changes with the raising and the
// clearing of its `root-not-free` condition. They are the condition keeper's (mesh-conditions) alone, the one keeper
// since the controller ended by its unassignment (novox/hq ADR 0590 §3, which ends ADR 0564 §9's selection by the
// take-over key).
const (
	EventKeeperRaised  = health.KeeperModule + ".condition-raised"
	EventKeeperCleared = health.KeeperModule + ".condition-cleared"
	// KindRootNotFree is the condition kind whose events wake a pass.
	KindRootNotFree = "root-not-free"
)

// FromKeeper says a condition event heard is the keeper's, by its name (`<seat>.<event>`) or its bus subject
// (`mesh.seat.<seat>.event.<event>`).
func FromKeeper(event string) bool {
	return strings.HasPrefix(event, health.KeeperModule+".") || strings.HasPrefix(event, "mesh.seat."+health.KeeperModule+".event.")
}

// EventAccountIssued is the vault's word that it minted an account (novox/hq ADR 0561 §1): its hash is in the vault's
// bus-accounts, so a pass composes the list with it.
const EventAccountIssued = "mesh-vault." + buscompose.AccountIssuedEvent

// Consumes is every event the part hears, as its manifest's consumes name them.
var Consumes = []string{EventKeeperRaised, EventKeeperCleared, EventAccountIssued}

// IsAccountIssued says an event heard is the vault's account-issued, by its name or its bus subject.
func IsAccountIssued(event string) bool {
	return event == EventAccountIssued || event == buscompose.AccountIssuedSubject
}

// IsRootNotFree says a condition event's body names the `root-not-free` kind (its `kind`, or the last part of its
// `key`, `<scope>.<id>.<kind>`). An unreadable body wakes a pass too: a pass is cheap, a missed change is not.
func IsRootNotFree(body []byte) bool {
	var c struct {
		Kind string `json:"kind"`
		Key  string `json:"key"`
	}
	if json.Unmarshal(body, &c) != nil {
		return true
	}
	return c.Kind == KindRootNotFree || (c.Kind == "" && strings.HasSuffix(c.Key, "."+KindRootNotFree)) || (c.Kind == "" && c.Key == "")
}

// RootFreeNodes are the machines a composition needs a root-free word for: where the router's seat is held and where a
// kinded seat's holder declares `verified-sender`. None when no holder declares it. Sorted. Pure.
func RootFreeNodes(r buscompose.Records) []string {
	var nodes []string
	need := false
	for node, declared := range r.Assigned {
		for _, d := range declared {
			for _, s := range d.Holds {
				if s.Name == "operator-channel" && !slices.Contains(nodes, node) {
					nodes = append(nodes, node)
				}
				if s.Kinded && s.Kind != "" && slices.Contains(s.Capabilities, "verified-sender") {
					need = true
					if !slices.Contains(nodes, node) {
						nodes = append(nodes, node)
					}
				}
			}
		}
	}
	if !need {
		return nil
	}
	sort.Strings(nodes)
	return nodes
}

// verdict is one machine's answer of its engine's root-free verb.
type verdict struct {
	Machine string `json:"machine"`
	Free    bool   `json:"free"`
	Why     string `json:"why"`
}

// WithRootFree fills r.RootFree for the machines the composition needs by asking each machine's own engine about that
// machine, and answers a line for each machine that is not free, `<machine>: <why>`. It fails closed: an error, no
// answer or a verdict an engine gives on another machine is not free, and says so. Pure but for the calls; the answers
// are kept for this pass alone.
func WithRootFree(r *buscompose.Records, call Caller) []string {
	nodes := RootFreeNodes(*r)
	if len(nodes) == 0 {
		return nil
	}
	free := map[string]verdict{}
	failures := map[string]string{}
	for _, n := range nodes {
		if call == nil {
			failures[n] = "no way to ask the machine's engine here"
			continue
		}
		raw, err := call.Call(CallRootFree+"@"+n, map[string]any{})
		if err != nil {
			failures[n] = "the engine's root-free word could not be asked: " + err.Error()
			continue
		}
		var body struct {
			Machines []verdict `json:"machines"`
		}
		if err := json.Unmarshal(raw, &body); err != nil {
			failures[n] = "the engine's root-free answer could not be read: " + err.Error()
			continue
		}
		for _, v := range body.Machines {
			if v.Machine == n {
				free[n] = v
			}
		}
	}
	r.RootFree = map[string]bool{}
	var notes []string
	for _, n := range nodes {
		v, answered := free[n]
		switch {
		case answered && v.Free:
			r.RootFree[n] = true
		case failures[n] != "":
			notes = append(notes, fmt.Sprintf("%s: not free, %s", n, failures[n]))
		case !answered:
			notes = append(notes, fmt.Sprintf("%s: not free, its engine named no verdict for it", n))
		default:
			notes = append(notes, fmt.Sprintf("%s: not free, %s", n, v.Why))
		}
	}
	return notes
}