dchain/contracts/counter/main.go

// Counter smart contract — compiles to WASM with GOOS=wasip1 GOARCH=wasm.
//
// Methods (exported via //go:export):
//   - increment  — adds 1 to the stored counter
//   - get        — logs the current value (readable via /api/contracts/{id}/state/counter)
//   - reset      — resets counter to 0; only the first caller (owner) is allowed
//
// Host imports from the "env" module (see vm/host.go):
//   - put_u64(keyPtr, keyLen, val)          — stores uint64 as 8-byte big-endian
//   - get_u64(keyPtr, keyLen) uint64        — reads 8-byte big-endian uint64
//   - get_caller(buf, bufLen) int32         — writes caller pub key hex into buf
//   - get_state(kPtr,kLen,dPtr,dLen) int32  — reads raw state bytes
//   - set_state(kPtr,kLen,vPtr,vLen)        — writes raw state bytes
//   - log(msgPtr, msgLen)                   — emits message to node log
//
//go:build wasip1

package main

import (
	"unsafe"
)

// ── host function imports ─────────────────────────────────────────────────────

//go:wasmimport env put_u64
func hostPutU64(keyPtr unsafe.Pointer, keyLen int32, val uint64)

//go:wasmimport env get_u64
func hostGetU64(keyPtr unsafe.Pointer, keyLen int32) uint64

//go:wasmimport env get_caller
func hostGetCaller(buf unsafe.Pointer, bufLen int32) int32

//go:wasmimport env get_state
func hostGetState(keyPtr unsafe.Pointer, keyLen int32, dstPtr unsafe.Pointer, dstLen int32) int32

//go:wasmimport env set_state
func hostSetState(keyPtr unsafe.Pointer, keyLen int32, valPtr unsafe.Pointer, valLen int32)

//go:wasmimport env log
func hostLog(msgPtr unsafe.Pointer, msgLen int32)

// ── helpers ───────────────────────────────────────────────────────────────────

func logMsg(s string) {
	if len(s) == 0 {
		return
	}
	b := []byte(s)
	hostLog(unsafe.Pointer(&b[0]), int32(len(b)))
}

func putU64(key string, val uint64) {
	b := []byte(key)
	hostPutU64(unsafe.Pointer(&b[0]), int32(len(b)), val)
}

func getU64(key string) uint64 {
	b := []byte(key)
	return hostGetU64(unsafe.Pointer(&b[0]), int32(len(b)))
}

func getState(key string, dst []byte) int32 {
	kb := []byte(key)
	return hostGetState(unsafe.Pointer(&kb[0]), int32(len(kb)),
		unsafe.Pointer(&dst[0]), int32(len(dst)))
}

func setState(key string, val []byte) {
	kb := []byte(key)
	hostSetState(unsafe.Pointer(&kb[0]), int32(len(kb)),
		unsafe.Pointer(&val[0]), int32(len(val)))
}

func getCaller() string {
	buf := make([]byte, 128)
	n := hostGetCaller(unsafe.Pointer(&buf[0]), int32(len(buf)))
	if n <= 0 {
		return ""
	}
	return string(buf[:n])
}

// ── contract state keys ───────────────────────────────────────────────────────

const (
	keyCounter = "counter"
	keyOwner   = "owner"
)

// ── exported contract methods ─────────────────────────────────────────────────

//go:export increment
func increment() {
	val := getU64(keyCounter)
	val++
	putU64(keyCounter, val)
	logMsg("incremented")
}

//go:export get
func get() {
	logMsg("get called")
}

//go:export reset
func reset() {
	caller := getCaller()
	if caller == "" {
		logMsg("reset: no caller")
		return
	}

	ownerBuf := make([]byte, 128)
	ownerLen := getState(keyOwner, ownerBuf)

	if ownerLen == 0 {
		// No owner set yet — first caller becomes the owner.
		setState(keyOwner, []byte(caller))
		putU64(keyCounter, 0)
		logMsg("reset ok (owner set)")
		return
	}

	owner := string(ownerBuf[:ownerLen])
	if caller != owner {
		logMsg("reset: unauthorized")
		return
	}

	putU64(keyCounter, 0)
	logMsg("reset ok")
}

// main is required by the Go runtime for wasip1 programs.
func main() {}