package busstate

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

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

// serveRuntime runs a bundle whose tool `go` runs fn in a goroutine and answers every call the bundle makes through handle,
// until done is closed by fn returning.
func serveRuntime(t *testing.T, fn func(), handle func(method string, params map[string]any) any) {
	t.Helper()
	t.Setenv(stdio.ServedAs, "distribution")
	inR, inW := io.Pipe()
	outR, outW := io.Pipe()
	done := make(chan struct{})
	go func() {
		_ = stdio.ServeOn("", []stdio.Tool{{Name: "go", Run: func(map[string]any) (any, error) {
			go func() { fn(); close(done) }()
			return "started", nil
		}}}, inR, outW)
	}()
	t.Cleanup(func() { _ = inW.Close() })
	lines := bufio.NewScanner(outR)
	lines.Buffer(make([]byte, 0, 1<<20), 64<<20)
	send := func(m map[string]any) { b, _ := json.Marshal(m); _, _ = inW.Write(append(b, '\n')) }
	send(map[string]any{"jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": map[string]any{"name": "go"}})
	deadline := time.After(10 * time.Second)
	for {
		got := make(chan map[string]any, 1)
		go func() {
			if lines.Scan() {
				var m map[string]any
				_ = json.Unmarshal(lines.Bytes(), &m)
				got <- m
			}
		}()
		select {
		case <-done:
			return
		case <-deadline:
			t.Fatal("the bundle did not finish")
		case m := <-got:
			method, _ := m["method"].(string)
			if method == "" {
				continue
			}
			p, _ := m["params"].(map[string]any)
			send(map[string]any{"jsonrpc": "2.0", "id": m["id"], "result": handle(method, p)})
		}
	}
}

// Design 47 G §518, §345, §490 (A-21): a value larger than one chunk is put as chunks in order under one call id, each
// answered before the next, with the store named in each; a get the runtime answers as a session is read chunk by chunk and
// checked against its digest.
func subAValueLargerThanOneChunkIsPutAndGotBySession(t *testing.T) {
	value := bytes.Repeat([]byte("0123456789abcdef"), (2*buscalls.ChunkBytes+1000)/16)
	sum := sha256.Sum256(value)
	digest := "sha256:" + hex.EncodeToString(sum[:])
	var stored []byte
	var seqs []uint32
	calls := map[string]bool{}
	var gotValue []byte
	var putErr, getErr, tamperErr error
	var tampered bool
	serveRuntime(t, func() {
		o := ObjectsOf("incoming")
		_, putErr = o.Put("big", value, "a big one")
		d, err := o.Get("big")
		gotValue, getErr = d.Data, err
		tampered = true
		_, tamperErr = o.Get("big")
	}, func(method string, p map[string]any) any {
		switch method {
		case stdio.CapabilitiesCall:
			return map[string]any{"words": []string{stdio.CapPutSessions}}
		case buscalls.ObjectsPutChunk:
			calls[p["call"].(string)] = true
			if p["objects"] != "incoming" || p["name"] != "big" {
				t.Errorf("a chunk named %v in %v", p["name"], p["objects"])
			}
			raw, _ := json.Marshal(p["data"])
			var b []byte
			_ = json.Unmarshal(raw, &b)
			if (p["description"] == "a big one") != (p["seq"].(float64) == 1) {
				t.Errorf("chunk %v carries the description %v: the first chunk alone does", p["seq"], p["description"])
			}
			stored = append(stored, b...)
			seqs = append(seqs, uint32(p["seq"].(float64)))
			if p["last"] == true {
				return buscalls.ObjectInfo{Name: "big", Size: uint64(len(stored))}
			}
			return buscalls.ObjectsChunkTaken{Seq: uint32(p["seq"].(float64))}
		case buscalls.ObjectsGet:
			d := digest
			if tampered {
				d = "sha256:" + hex.EncodeToString(make([]byte, 32))
			}
			return map[string]any{"chunked": 3, "size": len(stored), "digest": d, "call": "g1"}
		case buscalls.ObjectsGetChunk:
			seq := int(p["seq"].(float64))
			at := (seq - 1) * buscalls.ChunkBytes
			return buscalls.ObjectsChunk{Seq: uint32(seq), Last: seq == 3, Data: stored[at:min(at+buscalls.ChunkBytes, len(stored))]}
		}
		t.Errorf("unexpected call %s", method)
		return nil
	})
	if putErr != nil || getErr != nil {
		t.Fatalf("put %v, get %v", putErr, getErr)
	}
	if len(seqs) != 3 || seqs[0] != 1 || seqs[1] != 2 || seqs[2] != 3 || len(calls) != 1 || !bytes.Equal(stored, value) || !bytes.Equal(gotValue, value) {
		t.Errorf("chunks %v under %d call ids, stored %d bytes, got %d", seqs, len(calls), len(stored), len(gotValue))
	}
	if tamperErr == nil {
		t.Error("a value that is not the one the runtime named by its digest was accepted")
	}
}