```bash
#!/usr/bin/env bash
# ============================================================
# SUBTC GATEWAY V4.2 — Bitcoin Only
# Full curl reference
# SUBTC Protocol — Bitcoin curl API
# Gateway V4.2  ·  Bitcoin Only  ·  Stateless · Idempotent · curl-first
# API CURL POST ONLY : https://subtc.net/api
# ============================================================

BASE="https://api.subtc.net"

# ─────────────────────────────────────────────
# Health
# ─────────────────────────────────────────────
curl -sS "$BASE/health"

# ─────────────────────────────────────────────
# Key
# ─────────────────────────────────────────────
RESP=$(curl -sS -X POST "$BASE/v1/btc?mode=key_create" \
  -H "Content-Type: application/json")
KEY=$(echo "$RESP" | sed -n 's/.*"key":"\([^"]*\)".*/\1/p')
echo "KEY=$KEY"

curl -sS -X POST "$BASE/v1/btc?mode=key_status" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json"

# ─────────────────────────────────────────────
# Wallet
# ─────────────────────────────────────────────
RESP=$(curl -sS -X POST "$BASE/v1/btc?mode=wallet_create" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json" \
  -d '{"net":"test"}')
WID=$(echo "$RESP" | sed -n 's/.*"wallet_id":"\([^"]*\)".*/\1/p')
echo "WID=$WID"

curl -sS -X POST "$BASE/v1/btc?mode=wallet_list" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json"

# ─────────────────────────────────────────────
# Address
# ─────────────────────────────────────────────
RESP=$(curl -sS -X POST "$BASE/v1/btc?mode=wallet_receive" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json" \
  -d "{\"wallet_id\":\"$WID\"}")
ADDR=$(echo "$RESP" | sed -n 's/.*"address":"\([^"]*\)".*/\1/p')
echo "ADDR=$ADDR"

# ─────────────────────────────────────────────
# Balance
# ─────────────────────────────────────────────
curl -sS -X POST "$BASE/v1/btc?mode=wallet_balance" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json" \
  -d "{\"wallet_id\":\"$WID\"}"

# ─────────────────────────────────────────────
# Send
# ─────────────────────────────────────────────
curl -sS -X POST "$BASE/v1/btc?mode=wallet_send" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "X-SUBTC-IDEMPOTENCY: send-$(date +%s)" \
  -H "Content-Type: application/json" \
  -d "{\"wallet_id\":\"$WID\",\"to\":\"tb1qDESTINATION\",\"amount_sat\":50000}"

# ─────────────────────────────────────────────
# Inbox
# ─────────────────────────────────────────────
curl -sS -X POST "$BASE/v1/btc?mode=inbox_create" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json" \
  -d "{\"wallet_id\":\"$WID\",\"expected_sat\":20000}"

# ─────────────────────────────────────────────
# Wait — Long Poll
# ─────────────────────────────────────────────
curl -sS -X POST "$BASE/v1/btc?mode=wallet_wait_event" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json" \
  -d "{\"wallet_id\":\"$WID\",\"address\":\"$ADDR\",\"expected_sat\":20000,\"timeout_sec\":300}"

# ─────────────────────────────────────────────
# Wait — Webhook
# ─────────────────────────────────────────────
curl -sS -X POST "$BASE/v1/btc?mode=wallet_wait_event" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json" \
  -d "{\"wallet_id\":\"$WID\",\"address\":\"$ADDR\",\"expected_sat\":20000,\"timeout_sec\":600,\"callback_url\":\"https://yourserver.com/webhook\"}"

# ─────────────────────────────────────────────
# Poll — Single Check
# ─────────────────────────────────────────────
curl -sS -X POST "$BASE/v1/btc?mode=wallet_poll" \
  -H "X-SUBTC-KEY: $KEY" \
  -H "Content-Type: application/json" \
  -d "{\"wallet_id\":\"$WID\",\"address\":\"$ADDR\",\"expected_sat\":20000}"

# ─────────────────────────────────────────────
# Poll — Loop
# ─────────────────────────────────────────────
while true; do
  RESP=$(curl -sS -X POST "$BASE/v1/btc?mode=wallet_poll" \
    -H "X-SUBTC-KEY: $KEY" \
    -H "Content-Type: application/json" \
    -d "{\"wallet_id\":\"$WID\",\"address\":\"$ADDR\",\"expected_sat\":20000}")
  REACHED=$(echo "$RESP" | sed -n 's/.*"reached":\([a-z]*\).*/\1/p')
  RECEIVED=$(echo "$RESP" | sed -n 's/.*"received_sat":\([0-9]*\).*/\1/p')
  echo "received=$RECEIVED reached=$REACHED"
  [ "$REACHED" = "true" ] && echo "✅ confirmed" && break
  sleep 3
done
```
# Atomic Units & Fee Philosophy
# 1 BTC = 100,000,000 sat
# SUBTC uses integer atomic units for BTC
# Min send amounts:
# BTC: 50,000 SAT
# Service + network fee: 3%
# Deterministic rounding, idempotency, simplified auditing