package runtime

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"io"
	"strings"
	"testing"
	"time"

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

// fakeObjects is the bus of a session: what was put whole, what a read gives, and what the store deleted.
type fakeObjects struct {
	put         map[string][]byte
	description string
	deleted     []string
	read        []byte
	ctxEnded    chan struct{}
}

func (f *fakeObjects) ObjectsPutStream(ctx context.Context, _ string, r buscalls.ObjectsNameRequest, description string, in io.Reader) (buscalls.ObjectInfo, error) {
	data, err := io.ReadAll(in)
	if err != nil {
		f.deleted = append(f.deleted, r.Name)
		if f.ctxEnded != nil {
			<-ctx.Done()
			close(f.ctxEnded)
		}
		return buscalls.ObjectInfo{}, err
	}
	f.put[r.Name], f.description = data, description
	return buscalls.ObjectInfo{Name: r.Name, Size: uint64(len(data)), Description: description}, nil
}

func (f *fakeObjects) ObjectsOpen(context.Context, string, buscalls.ObjectsNameRequest) (buscalls.ObjectInfo, io.ReadCloser, bool, error) {
	return buscalls.ObjectInfo{Name: "o", Size: uint64(len(f.read))}, io.NopCloser(bytes.NewReader(f.read)), true, nil
}

func (f *fakeObjects) SentOpen(context.Context, buscalls.ObjectsSentGetRequest) (buscalls.ObjectInfo, io.ReadCloser, error) {
	return buscalls.ObjectInfo{Size: uint64(len(f.read))}, io.NopCloser(bytes.NewReader(f.read)), nil
}

func aSession(t *testing.T, f *fakeObjects) *moduleBus {
	t.Helper()
	c := &consumers{}
	c.sessions.store = f
	return &moduleBus{all: c, module: "m"}
}

func asked(t *testing.T, b *moduleBus, method string, req any, into any) {
	t.Helper()
	params, _ := json.Marshal(req)
	raw, err := b.BusState(method, params)
	if err != nil {
		t.Fatalf("%s: %v", method, err)
	}
	if err := json.Unmarshal(raw, into); err != nil {
		t.Fatal(err)
	}
}

// §490, §518, §620: a value over one chunk is got as a session (the chunked answer, then each chunk by its call and sequence,
// the whole checked against the digest); a sent object over one chunk the same, with `chunked` true.
func TestAGetOverOneChunkRunsAsASession(t *testing.T) {
	whole := bytes.Repeat([]byte("y"), 2*buscalls.ChunkBytes)
	f := &fakeObjects{read: whole}
	b := aSession(t, f)
	sum := sha256.Sum256(whole)
	want := "sha256:" + hex.EncodeToString(sum[:])
	for name, run := range map[string]func() buscalls.ObjectsChunked{
		"state": func() buscalls.ObjectsChunked {
			var c buscalls.ObjectsChunked
			asked(t, b, buscalls.ObjectsGet, buscalls.ObjectsNameRequest{Objects: "files", Name: "o"}, &c)
			return c
		},
		"sent": func() buscalls.ObjectsChunked {
			var c buscalls.ObjectsChunked
			asked(t, b, buscalls.ObjectsSentGet, buscalls.ObjectsSentGetRequest{Store: "m_sent-objects", Object: "o", Size: int64(len(whole)), Digest: hex.EncodeToString(sum[:])}, &c)
			if string(c.Chunked) != "true" {
				t.Errorf("a sent object's chunked is %s", c.Chunked)
			}
			return c
		},
	} {
		t.Run(name, func(t *testing.T) {
			c := run()
			if c.Call == "" || c.Size != uint64(len(whole)) {
				t.Fatalf("the get answered %+v", c)
			}
			if name == "state" {
				if string(c.Chunked) != "2" {
					t.Errorf("chunked is %s, want 2", c.Chunked)
				}
			}
			var got []byte
			for seq := uint32(1); ; seq++ {
				var ch buscalls.ObjectsChunk
				asked(t, b, buscalls.ObjectsGetChunk, buscalls.ObjectsGetChunkRequest{Call: c.Call, Seq: seq}, &ch)
				if ch.Error != "" || ch.Seq != seq {
					t.Fatalf("chunk %d: %+v", seq, ch)
				}
				got = append(got, ch.Data...)
				if ch.Last {
					if seq != 2 {
						t.Fatalf("an object of two chunks ended at chunk %d", seq)
					}
					break
				}
			}
			if !bytes.Equal(got, whole) || name == "state" && c.Digest == "" {
				t.Fatalf("read %d bytes, digest %s", len(got), c.Digest)
			}
			if name == "sent" && c.Digest != want {
				t.Errorf("digest %s, want %s", c.Digest, want)
			}
			var again buscalls.ObjectsChunk
			asked(t, b, buscalls.ObjectsGetChunk, buscalls.ObjectsGetChunkRequest{Call: c.Call, Seq: 3}, &again)
			if again.Error == "" {
				t.Error("a finished session answered another chunk")
			}
		})
	}
	// A value of one chunk or less is the value itself, as before.
	f.read = []byte("small")
	var small buscalls.ObjectData
	asked(t, b, buscalls.ObjectsGet, buscalls.ObjectsNameRequest{Objects: "files", Name: "o"}, &small)
	if string(small.Data) != "small" {
		t.Fatalf("a small value was answered %+v", small)
	}
	// Design 47 G §518, A-21, A-25: a put session writes each chunk as it is taken, carries the description of its first chunk,
	// and answers the put's own info for the last; a chunk out of order fails the put naming both sequences and leaves none.
	t.Run("APutSessionSealsOnTheLastChunkAndDropsOnADisorder", func(t *testing.T) {
		f := &fakeObjects{put: map[string][]byte{}}
		b := aSession(t, f)
		whole := bytes.Repeat([]byte("x"), 2*buscalls.ChunkBytes+5)
		var taken buscalls.ObjectsChunkTaken
		for seq, at := uint32(1), 0; ; seq++ {
			end := min(at+buscalls.ChunkBytes, len(whole))
			req := buscalls.ObjectsPutChunkRequest{Objects: "files", Name: "a", Call: "c1", Seq: seq, Last: end == len(whole), Data: whole[at:end]}
			if seq == 1 {
				req.Description = "what it is"
			}
			if req.Last {
				var info buscalls.ObjectInfo
				asked(t, b, buscalls.ObjectsPutChunk, req, &info)
				if info.Size != uint64(len(whole)) || info.Description != "what it is" {
					t.Fatalf("the put answered %+v", info)
				}
				break
			}
			asked(t, b, buscalls.ObjectsPutChunk, req, &taken)
			if taken.Seq != seq || taken.Error != "" {
				t.Fatalf("chunk %d was answered %+v", seq, taken)
			}
			at = end
		}
		if !bytes.Equal(f.put["a"], whole) {
			t.Fatalf("the store holds %d bytes, want %d", len(f.put["a"]), len(whole))
		}

		asked(t, b, buscalls.ObjectsPutChunk, buscalls.ObjectsPutChunkRequest{Objects: "files", Name: "b", Call: "c2", Seq: 1, Data: []byte("one")}, &taken)
		asked(t, b, buscalls.ObjectsPutChunk, buscalls.ObjectsPutChunkRequest{Objects: "files", Name: "b", Call: "c2", Seq: 3, Data: []byte("three")}, &taken)
		if !strings.Contains(taken.Error, "chunk 3") || !strings.Contains(taken.Error, "chunk 2") {
			t.Fatalf("a disorder was answered %+v", taken)
		}
		if _, ok := f.put["b"]; ok || len(f.deleted) != 1 || f.deleted[0] != "b" {
			t.Fatalf("a dropped put left %v, deleted %v", f.put, f.deleted)
		}
		asked(t, b, buscalls.ObjectsPutChunk, buscalls.ObjectsPutChunkRequest{Objects: "files", Name: "b", Call: "c2", Seq: 2, Data: []byte("two")}, &taken)
		if taken.Error == "" {
			t.Fatal("a chunk of a dropped put was taken")
		}
	})
	// §518 "The bound": a put not sealed within the bound is dropped, its object deleted.
	t.Run("APutNotSealedWithinTheBoundIsDropped", func(t *testing.T) {
		was := SessionBound
		SessionBound = time.Millisecond
		t.Cleanup(func() { SessionBound = was })
		f := &fakeObjects{put: map[string][]byte{}, ctxEnded: make(chan struct{})}
		b := aSession(t, f)
		var taken buscalls.ObjectsChunkTaken
		asked(t, b, buscalls.ObjectsPutChunk, buscalls.ObjectsPutChunkRequest{Objects: "files", Name: "a", Call: "c", Seq: 1, Data: []byte("x")}, &taken)
		<-f.ctxEnded
		if len(f.deleted) != 1 {
			t.Fatalf("the unsealed object was left: %v", f.deleted)
		}
	})
}