#!/bin/bash
# Traffic switching script for blue-green deployment
# Updates Traefik weighted routing configuration
#
# Usage: ./switch-traffic.sh <target_stack> [mode]
#   target_stack: blue or green (the stack to switch TO)
#   mode: instant (default) or gradual
#
# Gradual mode: 25% -> 50% -> 75% -> 100% with 3s intervals
#
# Exit codes:
#   0 - Traffic switch successful
#   1 - Switch failed

set -euo pipefail

# Use DEPLOY_PATH if set (CI environment), otherwise calculate from script location
# This is critical: CI workflows must pass DEPLOY_PATH to ensure we modify
# the actual deployment config, not the checkout directory
PROJECT_ROOT="${DEPLOY_PATH:-$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)}"

echo "Using PROJECT_ROOT: $PROJECT_ROOT"

TARGET_STACK="${1:-}"
MODE="${2:-instant}"

if [[ -z "$TARGET_STACK" ]] || [[ ! "$TARGET_STACK" =~ ^(blue|green)$ ]]; then
  echo "Usage: $0 <blue|green> [instant|gradual]"
  exit 1
fi

TRAEFIK_CONFIG="$PROJECT_ROOT/config/traefik/dynamic/blue-green.yml"
STATE_FILE="$PROJECT_ROOT/config/deployment/state.json"

if [[ ! -f "$TRAEFIK_CONFIG" ]]; then
  echo "ERROR: Traefik config not found: $TRAEFIK_CONFIG"
  exit 1
fi

echo "========================================"
echo "Traffic Switch"
echo "Target Stack: $TARGET_STACK"
echo "Mode: $MODE"
echo "========================================"

# Determine source and target weights
if [[ "$TARGET_STACK" == "blue" ]]; then
  SOURCE_STACK="green"
else
  SOURCE_STACK="blue"
fi

# Function to update weights in Traefik config
update_weights() {
  local blue_weight="$1"
  local green_weight="$2"

  echo "  Setting weights: blue=$blue_weight, green=$green_weight"

  # YAML structure has name and weight on separate lines:
  #   - name: mvp-frontend-blue-svc
  #     weight: 100
  # Use awk for reliable multi-line pattern matching (more portable than sed)
  # Match "- name: service-name" to avoid matching the loadBalancer section

  awk -v blue="$blue_weight" -v green="$green_weight" '
    /- name: mvp-frontend-blue-svc$/ {print; getline; sub(/weight: [0-9]+/, "weight: " blue); print; next}
    /- name: mvp-frontend-green-svc$/ {print; getline; sub(/weight: [0-9]+/, "weight: " green); print; next}
    /- name: mvp-backend-blue-svc$/ {print; getline; sub(/weight: [0-9]+/, "weight: " blue); print; next}
    /- name: mvp-backend-green-svc$/ {print; getline; sub(/weight: [0-9]+/, "weight: " green); print; next}
    {print}
  ' "$TRAEFIK_CONFIG" > "${TRAEFIK_CONFIG}.tmp" && mv "${TRAEFIK_CONFIG}.tmp" "$TRAEFIK_CONFIG"

  # Traefik watches the file and reloads automatically
  # Give it a moment to pick up changes
  sleep 1
}

# Verify weights were actually written to config file
verify_weights_applied() {
  local expected_blue="$1"
  local expected_green="$2"

  # Extract actual weights from the config file
  local actual_blue=$(grep -A1 "mvp-frontend-blue-svc" "$TRAEFIK_CONFIG" | grep weight | grep -oE '[0-9]+' | head -1)
  local actual_green=$(grep -A1 "mvp-frontend-green-svc" "$TRAEFIK_CONFIG" | grep weight | grep -oE '[0-9]+' | head -1)

  if [[ "$actual_blue" != "$expected_blue" ]] || [[ "$actual_green" != "$expected_green" ]]; then
    echo "  ERROR: Weight verification failed!"
    echo "  Expected: blue=$expected_blue, green=$expected_green"
    echo "  Actual: blue=$actual_blue, green=$actual_green"
    echo "  Config file: $TRAEFIK_CONFIG"
    return 1
  fi

  echo "  OK: Weights verified (blue=$actual_blue, green=$actual_green)"
  return 0
}

# Verify Traefik has picked up the changes
verify_traefik_reload() {
  # Give Traefik time to reload config
  sleep 2

  # Check if Traefik is still healthy
  if docker exec mvp-traefik traefik healthcheck > /dev/null 2>&1; then
    echo "  OK: Traefik config reloaded"
    return 0
  else
    echo "  WARNING: Could not verify Traefik health"
    return 0  # Don't fail on this, file watcher is reliable
  fi
}

if [[ "$MODE" == "gradual" ]]; then
  echo ""
  echo "Gradual traffic switch starting..."
  echo "----------------------------------------"

  if [[ "$TARGET_STACK" == "blue" ]]; then
    STEPS=("25 75" "50 50" "75 25" "100 0")
  else
    STEPS=("75 25" "50 50" "25 75" "0 100")
  fi

  step=1
  for weights in "${STEPS[@]}"; do
    blue_w=$(echo "$weights" | cut -d' ' -f1)
    green_w=$(echo "$weights" | cut -d' ' -f2)

    echo ""
    echo "Step $step/4: blue=$blue_w%, green=$green_w%"
    update_weights "$blue_w" "$green_w"
    verify_traefik_reload

    if [[ $step -lt 4 ]]; then
      echo "  Waiting 3 seconds before next step..."
      sleep 3
    fi

    step=$((step + 1))
  done

else
  # Instant switch
  echo ""
  echo "Instant traffic switch..."
  echo "----------------------------------------"

  if [[ "$TARGET_STACK" == "blue" ]]; then
    update_weights 100 0
    verify_weights_applied 100 0 || exit 1
  else
    update_weights 0 100
    verify_weights_applied 0 100 || exit 1
  fi

  verify_traefik_reload
fi

# Update state file
echo ""
echo "Updating deployment state..."
echo "----------------------------------------"

if [[ -f "$STATE_FILE" ]] && command -v jq &> /dev/null; then
  TIMESTAMP=$(date -u +"%Y-%m-%dT%H:%M:%SZ")

  jq --arg active "$TARGET_STACK" \
     --arg inactive "$SOURCE_STACK" \
     --arg ts "$TIMESTAMP" \
     '.active_stack = $active | .inactive_stack = $inactive | .last_switch = $ts' \
     "$STATE_FILE" > "${STATE_FILE}.tmp" && mv "${STATE_FILE}.tmp" "$STATE_FILE"

  echo "  Active stack: $TARGET_STACK"
  echo "  Inactive stack: $SOURCE_STACK"
fi

echo ""
echo "========================================"
echo "Traffic Switch COMPLETE"
echo "All traffic now routed to: $TARGET_STACK"
echo "========================================"

exit 0