// Package approval is the tool runner's gate on a call that needs the operator's approval (design 46 7-approval-mark): the
// marks it reads from the catalog half, the act it digests, the ask it raises on the seat operator-channel under the
// marked module's name, the judging of the same call again on the router's record, the claim, the recording in the
// hand-act log, and the refusals when a part of the check is missing (§5, §8 to §20). No module's name is written here.
package approval

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

	catalogseat "git.novox.be/novox/mesh-delivery/contracts/go/seats/meshcatalog"
	"git.novox.be/novox/mesh-sdk/go/buscompose"
	"git.novox.be/novox/mesh-sdk/go/seatdef"
)

// Catalog is what the marks are read from: the catalog half the runner follows (design 46 7-approval-mark §5, design 47 G
// §196, §443) and the seat definitions it carries (§2).
type Catalog interface {
	// Ready is nil once the catalog half's first view is read, else says what it waits for.
	Ready() error
	// Revision is the catalog revision the marks are read at, as the runner names it.
	Revision() string
	// Served is the entry of the build a bundle serves, by the fingerprint its composed environment carries; false when
	// none is read (not yet, or not found), with why.
	Served(fingerprint string) (catalogseat.CatalogEntry, bool, string)
	// Newest is the module's entry at the newest revision; false when the catalog half lists none.
	Newest(module string) (catalogseat.CatalogEntry, bool)
	// Definitions are the seat definitions the catalog half carries, by seat.
	Definitions() map[string]seatdef.Definition
	// Entries are the newest entry of every module in every followed branch's half, a marked wait's marks (lead answer
	// A-168).
	Entries() []catalogseat.CatalogEntry
}

// Marks is what one module's calls are gated by: its marked tools and seat verbs, and the subjects of its marked events and
// restricted streams, each with its source (§18: its module's entry in the catalog half, or its seat's definition).
type Marks struct {
	Module string
	// Tools are its marked tools by name, Verbs its marked seat verbs as `<seat>.<verb>`, Subjects the bus subjects of its
	// marked events and restricted streams (design 34 every-event §33); each to its source.
	Tools, Verbs, Subjects map[string]string
	// Revision is the catalog revision read; Served the served entry's fingerprint, empty when it could not be read.
	Revision, Served string
	// Unread says why the served entry could not be read: every marked call is then refused (§5, §19).
	Unread string
}

// Marked says whether a tool or a seat verb of the module needs the operator's approval, and its source.
func (m Marks) Marked(seat, name string) (bool, string) {
	if seat == "" {
		src, ok := m.Tools[name]
		return ok, src
	}
	src, ok := m.Verbs[seat+"."+name]
	return ok, src
}

// Any says the module marks anything at all.
func (m Marks) Any() bool { return len(m.Tools)+len(m.Verbs)+len(m.Subjects) > 0 }

// marked is what an entry's manifest says of its marks: `needs-approval`, its events and its streams.
type marked struct {
	NeedsApproval []string `json:"needs-approval"`
	Emits         []string `json:"emits"`
	// Streams are read for their events and whether each carries a `grant`, and no other word, so a word added to a
	// stream's declaration later never hides its marks.
	Streams []struct {
		Events []string        `json:"events"`
		Grant  json.RawMessage `json:"grant"`
	} `json:"streams"`
}

// Derive is a module's marks from its served entry and its newest one, unioned while they differ so a mark is never lost
// before or after the module moves (§5, ADR 0286 §3), and the seat definitions' verb marks for every verb an entry serves,
// which no holder unmarks (§2, §3). fingerprint is the build its bundle serves; empty, or an entry not read, leaves the
// marks of the newest entry and the seats, with Unread saying why.
func Derive(c Catalog, module, fingerprint string) Marks {
	m := Marks{Module: module, Tools: map[string]string{}, Verbs: map[string]string{}, Subjects: map[string]string{},
		Revision: c.Revision()}
	defs := c.Definitions()
	var entries []catalogseat.CatalogEntry
	if fingerprint == "" {
		m.Unread = "its bundle's environment carries no fingerprint, so the build it serves cannot be read"
	} else if e, ok, why := c.Served(fingerprint); ok {
		entries, m.Served = append(entries, e), fingerprint
	} else {
		m.Unread = fmt.Sprintf("the catalog half's entry of %s cannot be read: %s", fingerprint, why)
	}
	if e, ok := c.Newest(module); ok && (len(entries) == 0 || e.Fp != entries[0].Fp) {
		entries = append(entries, e)
	}
	for _, e := range entries {
		m.add(e, defs)
	}
	return m
}

// add takes one entry's marks into m: its `needs-approval` (a tool, a verb it serves or an event it declares), the seat
// definitions' marks of every verb it serves, and every stream it declares with a `grant`, each with its source.
func (m *Marks) add(e catalogseat.CatalogEntry, defs map[string]seatdef.Definition) {
	source := "entry " + e.Module + " " + orNone(e.Fp)
	var said marked
	if raw, err := json.Marshal(e.Manifest); err == nil {
		_ = json.Unmarshal(raw, &said)
	}
	serves := map[string]bool{}
	for _, sv := range e.Serves {
		serves[sv] = true
		seat, verb, _ := strings.Cut(sv, ".")
		for _, v := range defs[seat].Verbs {
			if v.Name == verb && v.NeedsApproval {
				m.Verbs[sv] = "seat " + seat
			}
		}
	}
	events := map[string]bool{}
	for _, ev := range said.Emits {
		events[ev] = true
	}
	for _, s := range said.Streams {
		for _, ev := range s.Events {
			events[ev] = true
		}
	}
	for _, name := range said.NeedsApproval {
		switch {
		case serves[name]:
			if _, bySeat := m.Verbs[name]; !bySeat {
				m.Verbs[name] = source
			}
		case events[name]:
			for _, s := range eventSubjects(e.Module, name) {
				m.Subjects[s] = source
			}
		default:
			m.Tools[name] = source
		}
	}
	for _, s := range said.Streams {
		if len(s.Grant) == 0 || string(s.Grant) == "null" {
			continue
		}
		wire := make([]string, 0, len(s.Events))
		for _, ev := range s.Events {
			wire = append(wire, buscompose.WirePattern(ev))
		}
		for _, sub := range (buscompose.ModuleStream{Module: e.Module, Events: wire}).Subjects() {
			m.Subjects[sub] = source
			if !strings.HasSuffix(sub, ">") {
				m.Subjects[sub+".>"] = source
			}
		}
	}
}

// eventSubjects are a marked event's subjects on the bus (design 34 every-event §33): said on the module's events and on its
// own stream, each also with every subject below it.
func eventSubjects(module, event string) []string {
	ev := buscompose.WirePattern(event)
	out := []string{"mesh.mod." + module + ".event." + ev, buscompose.ModuleStreamSubject(module, ev)}
	if !strings.HasSuffix(ev, ">") {
		out = append(out, out[0]+".>", out[1]+".>")
	}
	sort.Strings(out)
	return out
}

func orNone(s string) string {
	if s == "" {
		return "none"
	}
	return s
}

// keysOf is a set's names, sorted; nil when empty.
func keysOf(set map[string]string) []string {
	var out []string
	for k := range set {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}