package main

import (
	"fmt"
	"net"
	"sort"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"golang.org/x/net/dns/dnsmessage"

	"github.com/novox/mesh-controller/internal/conditions"
	"github.com/novox/mesh-controller/internal/inventory"
	"github.com/novox/mesh-controller/internal/outward"
)

// unsaid collects, across the suite, every finding whose words the operator's channel would withhold.
var unsaid unsayable

type unsayable struct {
	mu   sync.Mutex
	seen map[string]bool
}

func (u *unsayable) note(o conditions.Observation, field string, r outward.Refusal) {
	text := o.Summary
	if field == "key" {
		text = o.Key()
	}
	u.mu.Lock()
	defer u.mu.Unlock()
	if u.seen == nil {
		u.seen = map[string]bool{}
	}
	u.seen[fmt.Sprintf("%s (source %s, kind %s): its %s carries %s — %q", o.Key(), o.Source, o.Kind, field, r.What,
		text)] = true
}

func (u *unsayable) all() []string {
	u.mu.Lock()
	defer u.mu.Unlock()
	var out []string
	for s := range u.seen {
		out = append(out, s)
	}
	sort.Strings(out)
	return out
}

// unworded collects, across the suite, every finding said in borrowed words (ADR 0253).
var unworded wordless

type wordless struct {
	mu   sync.Mutex
	seen map[string]bool
}

func (u *wordless) add(o conditions.Observation, why string) {
	u.mu.Lock()
	defer u.mu.Unlock()
	if u.seen == nil {
		u.seen = map[string]bool{}
	}
	u.seen[fmt.Sprintf("kind %s (scope %s, source %s): %s", o.Kind, o.Scope, o.Source, why)] = true
}

func (u *wordless) all() []string {
	u.mu.Lock()
	defer u.mu.Unlock()
	var out []string
	for s := range u.seen {
		out = append(out, s)
	}
	sort.Strings(out)
	return out
}

// linted is a producer's findings, held to the content rule as a keeper would hold them: for a test
// that reads a producer's findings without raising them.
func linted(obs []conditions.Observation) []conditions.Observation {
	for _, o := range obs {
		machines := append([]string{o.Machine}, o.Also...)
		if r, ok := outward.Check(o.Key(), machines...); !ok {
			unsaid.note(o, "key", r)
		}
		if r, ok := outward.Check(o.Summary, machines...); !ok {
			unsaid.note(o, "summary", r)
		}
		switch {
		case o.Headline != "":
			w := conditions.Words{Headline: o.Headline, Explanation: o.Explanation, Resolved: o.Resolved}
			if w.Resolved == "" {
				w.Resolved = "Resolved"
			}
			if why, ok := conditions.PlainWords(w, machines...); !ok {
				unworded.add(o, "its source's words are not plain: "+why)
			}
		case o.Kind != "" && !conditions.Worded(o.Kind):
			unworded.add(o, "the kind "+o.Kind+" has no plain words")
		}
	}
	return obs
}

// resolverStandIn is a resolver on loopback that answers as answer says; nil answers nothing.
func resolverStandIn(t *testing.T, answer func(q dnsmessage.Question, n int64) *dnsmessage.Message) (port string, asked *atomic.Int64) {
	t.Helper()
	conn, err := net.ListenPacket("udp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = conn.Close() })
	asked = &atomic.Int64{}
	go func() {
		buf := make([]byte, 1500)
		for {
			n, from, err := conn.ReadFrom(buf)
			if err != nil {
				return
			}
			var q dnsmessage.Message
			if q.Unpack(buf[:n]) != nil || len(q.Questions) == 0 {
				continue
			}
			reply := answer(q.Questions[0], asked.Add(1))
			if reply == nil {
				continue
			}
			reply.Header.ID, reply.Header.Response, reply.Questions = q.ID, true, q.Questions
			packed, _ := reply.Pack()
			_, _ = conn.WriteTo(packed, from)
		}
	}()
	_, port, _ = net.SplitHostPort(conn.LocalAddr().String())
	return port, asked
}

// answersRightly answers A with the address the test's machine has, and NODATA for AAAA.
func answersRightly(q dnsmessage.Question) *dnsmessage.Message {
	reply := &dnsmessage.Message{}
	if q.Type == dnsmessage.TypeA {
		reply.Answers = []dnsmessage.Resource{{Header: dnsmessage.ResourceHeader{Name: q.Name, Type: dnsmessage.TypeA,
			Class: dnsmessage.ClassINET}, Body: &dnsmessage.AResource{A: [4]byte{10, 77, 0, 1}}}}
	}
	return reply
}

// quickResolvers makes D2's patience short for a test.
func quickResolvers(t *testing.T, port string) {
	t.Helper()
	before, within, pause := resolverPort, resolverWithin, resolverPause
	resolverPort, resolverWithin, resolverPause = port, 60*time.Millisecond, 5*time.Millisecond
	t.Cleanup(func() { resolverPort, resolverWithin, resolverPause = before, within, pause })
}

var anchorOnTheNetwork = []inventory.Overlay{{Name: "anchor", Address: "10.77.0.1"}}

// **D2 asks again before it says anything** (novox/hq issue 277): a resolver that misses a question on
// a loaded machine and answers the next try is a resolver that answers.
func TestAResolverThatMissesOneTryAndAnswersTheNextIsWell(t *testing.T) {
	port, asked := resolverStandIn(t, func(q dnsmessage.Question, n int64) *dnsmessage.Message {
		if n <= 2 {
			return nil // the first question of each kind lost, as under a push and a build starting
		}
		return answersRightly(q)
	})
	quickResolvers(t, port)
	got := askEveryResolver(t.Context(), map[string]string{"anchor.internal": "127.0.0.1"}, anchorOnTheNetwork, "internal")
	if len(got) != 0 {
		t.Fatalf("a resolver that answered its second try was said: %+v", got)
	}
	if asked.Load() < 3 {
		t.Fatalf("asked %d times", asked.Load())
	}
}

// **A resolver that answers nothing is held for the next run, and said in machine names**: the address
// it was asked at and the socket's words are the evidence, never the summary the operator reads.
func TestAResolverThatAnswersNothingIsHeldAndSaidInMachineNames(t *testing.T) {
	port, asked := resolverStandIn(t, func(dnsmessage.Question, int64) *dnsmessage.Message { return nil })
	quickResolvers(t, port)
	got := askEveryResolver(t.Context(), map[string]string{"anchor.internal": "127.0.0.1"}, anchorOnTheNetwork, "internal")
	if len(got) != 1 {
		t.Fatalf("%+v", got)
	}
	o := got[0]
	if !o.Confirm || o.Key() != "seat.mesh-dns-resolver.anchor.wrong" || o.Severity != conditions.Urgent {
		t.Fatalf("not held for a second look, or not the resolver's condition: %+v", o)
	}
	if r, ok := outward.Check(o.Summary, "anchor"); !ok {
		t.Fatalf("the summary carries %s: %q", r, o.Summary)
	}
	if !strings.Contains(o.Summary, "anchor's") || !strings.Contains(o.Said, "127.0.0.1") ||
		!strings.Contains(o.Said, "anchor.internal") {
		t.Fatalf("summary %q, evidence %q", o.Summary, o.Said)
	}
	if want := int64(2 * resolverTries); asked.Load() != want {
		t.Fatalf("asked %d times, want %d: each question %d times", asked.Load(), want, resolverTries)
	}
}

// **A resolver that answers wrongly is said at once**, in machine names: an answer is not the absence
// of one (issue 262's NXDOMAIN for IPv6).
func TestAResolverAnsweringWronglyIsSaidAtOnceInMachineNames(t *testing.T) {
	port, _ := resolverStandIn(t, func(q dnsmessage.Question, _ int64) *dnsmessage.Message {
		if q.Type == dnsmessage.TypeAAAA {
			return &dnsmessage.Message{Header: dnsmessage.Header{RCode: dnsmessage.RCodeNameError}}
		}
		return answersRightly(q)
	})
	quickResolvers(t, port)
	got := askEveryResolver(t.Context(), map[string]string{"anchor.internal": "127.0.0.1"}, anchorOnTheNetwork, "internal")
	if len(got) != 1 || got[0].Confirm {
		t.Fatalf("%+v", got)
	}
	if r, ok := outward.Check(got[0].Summary, "anchor"); !ok || !strings.Contains(got[0].Summary, "NXDOMAIN") ||
		!strings.Contains(got[0].Summary, "anchor's IPv6 address") {
		t.Fatalf("summary %q (%v)", got[0].Summary, r)
	}
}

// **The self-check raises a finding one look can be wrong about on the second run in a row**, keeps it
// open while it is seen, and clears it when it is not — and a probe that cannot run is said as a
// condition only when the next run cannot run it either. Neither is ever a pass in the verdict.