#!/bin/sh
set -eu

normalize_path() {
  value="${1:-}"
  value="/$(printf '%s' "$value" | sed -e 's#^/*##' -e 's#/*$##')"
  if [ "$value" = "/" ]; then
    printf ''
  else
    printf '%s' "$value"
  fi
}

external_path="$(normalize_path "${AISHARE_PROXY_EXTERNAL_PATH:-/aishare}")"
upstream_path="$(normalize_path "${AISHARE_UPSTREAM_PATH:-/aishare}")"
upstream_origin="$(printf '%s' "${AISHARE_UPSTREAM_ORIGIN:?set AISHARE_UPSTREAM_ORIGIN}" | sed -e 's#/*$##')"
listen_port="${AISHARE_PROXY_LISTEN:-8080}"
server_name="${AISHARE_PROXY_SERVER_NAME:-_}"
client_max_body_size="${AISHARE_PROXY_CLIENT_MAX_BODY_SIZE:-20m}"
external_slash="${external_path}/"
upstream_slash="${upstream_path}/"
if [ -z "$external_path" ]; then external_slash="/"; fi
if [ -z "$upstream_path" ]; then upstream_slash="/"; fi

cat > /etc/nginx/conf.d/default.conf <<EOF
server {
    listen ${listen_port};
    server_name ${server_name};

    client_max_body_size ${client_max_body_size};

    proxy_http_version 1.1;
    proxy_ssl_server_name on;
    proxy_set_header Host \$proxy_host;
    proxy_set_header X-Forwarded-Host \$http_host;
    proxy_set_header X-Forwarded-For \$proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto \$scheme;
    proxy_set_header X-Forwarded-Prefix ${external_path:-/};
    proxy_set_header X-Real-Ip \$remote_addr;
EOF

write_proxy_block() {
  location_line="$1"
  rewrite_line="$2"
  cat >> /etc/nginx/conf.d/default.conf <<EOF

    ${location_line} {
        ${rewrite_line}
        proxy_redirect ${upstream_slash} ${external_slash};
        proxy_redirect ${upstream_origin}${upstream_slash} \$scheme://\$http_host${external_slash};
        proxy_pass ${upstream_origin};
    }
EOF
}

if [ -z "$external_path" ]; then
  write_proxy_block "location /" "rewrite ^/(.*)\$ ${upstream_path}/\$1 break;"
else
  cat >> /etc/nginx/conf.d/default.conf <<EOF

    location = ${external_path} {
        return 301 ${external_path}/;
    }
EOF
  write_proxy_block "location ^~ ${external_path}/" "rewrite ^${external_path}/?(.*)\$ ${upstream_path}/\$1 break;"
fi

cat >> /etc/nginx/conf.d/default.conf <<'EOF'
}
EOF