#!/usr/bin/env bash
#
# GRU M1 Dominance Simulation (S0-S5)
# Simulates how GRU M1 supply affects BTC/ETH/Stablecoin dominance.
# Uses CoinGecko global API; falls back to env vars if API fails.
#
# Usage: ./dominance-simulation.sh [output_file]
#   output_file: optional path to write markdown report
#
# Env fallback (if API unavailable):
#   GRU_M1_TOTAL_MARKET_CAP   - total crypto market cap (USD)
#   GRU_M1_BTC_DOMINANCE      - BTC dominance %
#   GRU_M1_ETH_DOMINANCE      - ETH dominance %
#   GRU_M1_STABLECOIN_DOM     - stablecoin dominance %
#
set -e

COINGECKO_URL="${COINGECKO_URL:-https://api.coingecko.com/api/v3/global}"
SCENARIOS=(0 100000000 500000000 1000000000 5000000000 10000000000)
SCENARIO_LABELS=("S0" "S1" "S2" "S3" "S4" "S5")
SCENARIO_DESCS=("Baseline (no GRU M1)" "Pilot (\$100M)" "Early institutional (\$500M)" "Regional (\$1B)" "Multi-jurisdiction (\$5B)" "Systemic (\$10B)")

# Fetch baseline from CoinGecko
fetch_baseline() {
  if command -v curl >/dev/null 2>&1 && command -v jq >/dev/null 2>&1; then
    local json
    json=$(curl -sL --connect-timeout 10 "$COINGECKO_URL" 2>/dev/null) || return 1
    local total_usd
    total_usd=$(echo "$json" | jq -r '.data.total_market_cap.usd // empty')
    [[ -z "$total_usd" || "$total_usd" == "null" ]] && return 1
    local btc_pct eth_pct usdt_pct usdc_pct
    btc_pct=$(echo "$json" | jq -r '.data.market_cap_percentage.btc // 0')
    eth_pct=$(echo "$json" | jq -r '.data.market_cap_percentage.eth // 0')
    usdt_pct=$(echo "$json" | jq -r '.data.market_cap_percentage.usdt // 0')
    usdc_pct=$(echo "$json" | jq -r '.data.market_cap_percentage.usdc // 0')
    local stable_pct
    stable_pct=$(echo "$usdt_pct + $usdc_pct" | bc 2>/dev/null || echo "$usdt_pct $usdc_pct" | awk '{print $1+$2}')
    echo "${total_usd} ${btc_pct} ${eth_pct} ${stable_pct}"
    return 0
  fi
  return 1
}

# Use env fallback
env_baseline() {
  local total="${GRU_M1_TOTAL_MARKET_CAP:-2500000000000}"
  local btc="${GRU_M1_BTC_DOMINANCE:-54}"
  local eth="${GRU_M1_ETH_DOMINANCE:-18}"
  local stable="${GRU_M1_STABLECOIN_DOM:-10}"
  echo "${total} ${btc} ${eth} ${stable}"
}

# Format number for display (e.g. 2.5T, 100M)
fmt_num() {
  local n="$1"
  awk -v n="$n" 'BEGIN {
    if (n >= 1e12) printf "%.2fT", n/1e12
    else if (n >= 1e9) printf "%.2fB", n/1e9
    else if (n >= 1e6) printf "%.2fM", n/1e6
    else printf "%s", n
  }'
}

# Run simulation and output markdown
run_simulation() {
  local baseline
  baseline=$(fetch_baseline 2>/dev/null) || baseline=$(env_baseline)
  read -r total_usd btc_pct eth_pct stable_pct <<< "$baseline"

  # Derive caps from percentages (stablecoin cap = total * stable_pct/100)
  local btc_cap eth_cap stable_cap
  btc_cap=$(echo "scale=2; $total_usd * $btc_pct / 100" | bc 2>/dev/null || echo "$total_usd $btc_pct" | awk '{printf "%.2f", $1*$2/100}')
  eth_cap=$(echo "scale=2; $total_usd * $eth_pct / 100" | bc 2>/dev/null || echo "$total_usd $eth_pct" | awk '{printf "%.2f", $1*$2/100}')
  stable_cap=$(echo "scale=2; $total_usd * $stable_pct / 100" | bc 2>/dev/null || echo "$total_usd $stable_pct" | awk '{printf "%.2f", $1*$2/100}')

  local timestamp
  timestamp=$(date -u +"%Y-%m-%d %H:%M UTC" 2>/dev/null || date -u)

  echo "# GRU M1 Dominance Simulation Results"
  echo ""
  echo "**Generated:** $timestamp"
  echo ""
  echo "## Baseline (Reference Snapshot)"
  echo ""
  echo "| Variable | Value |"
  echo "| -------- | ----- |"
  echo "| Total Market Cap | \$$(fmt_num "$total_usd") |"
  echo "| BTC Dominance | ${btc_pct}% |"
  echo "| ETH Dominance | ${eth_pct}% |"
  echo "| Stablecoin Dominance | ${stable_pct}% |"
  echo ""
  echo "## Simulation Scenarios (S0-S5)"
  echo ""
  echo "| Scenario | Total Cap | Stablecoin Cap | BTC Dom % | ETH Dom % | Stablecoin Dom % |"
  echo "| -------- | --------- | -------------- | --------- | --------- | ---------------- |"

  for i in "${!SCENARIOS[@]}"; do
    local gru_m1="${SCENARIOS[$i]}"
    local new_total new_stable
    new_total=$(awk "BEGIN {printf \"%.2f\", $total_usd + $gru_m1}")
    new_stable=$(awk "BEGIN {printf \"%.2f\", $stable_cap + $gru_m1}")
    local btc_dom eth_dom stable_dom
    btc_dom=$(awk "BEGIN {printf \"%.2f\", $btc_cap / $new_total * 100}")
    eth_dom=$(awk "BEGIN {printf \"%.2f\", $eth_cap / $new_total * 100}")
    stable_dom=$(awk "BEGIN {printf \"%.2f\", $new_stable / $new_total * 100}")
    echo "| ${SCENARIO_LABELS[$i]} | \$$(fmt_num "$new_total") | \$$(fmt_num "$new_stable") | $btc_dom | $eth_dom | $stable_dom |"
  done

  echo ""
  echo "## Interpretation"
  echo ""
  echo "- BTC/ETH dominance declines mechanically as GRU M1 supply grows"
  echo "- Stablecoin dominance increases without volatility"
  echo "- No implication of speculative capital shift"
  echo "- Use **ex-M1 internal metrics** for risk analysis"
  echo ""
  echo "---"
  echo "See: [GRU M1 Real-Data Dominance Addendum](../../docs/gru-m1/GRU_M1_REAL_DATA_DOMINANCE_ADDENDUM.md)"
}

# Main
output_file="${1:-}"
if [[ -n "$output_file" ]]; then
  mkdir -p "$(dirname "$output_file")"
  run_simulation > "$output_file"
  echo "Report written to: $output_file"
else
  run_simulation
fi