#!/usr/bin/env bash
# fastget — universal aria2c wrapper with auto feature detection
# Usage:
#   fastget <url> [more_urls...]
#   fastget -o file.zip <url>
#   fastget --sane <url>    # less aggressive profile

set -euo pipefail

PROFILE="aggressive"
OUT_NAME=""
if [[ "${1:-}" == "--sane" ]]; then
  PROFILE="sane"
  shift
fi

while getopts ":o:" opt; do
  case "$opt" in
    o) OUT_NAME="$OPTARG" ;;
    *) echo "Usage: $0 [--sane] [-o output] <url> [more_urls...]"; exit 1 ;;
  esac
done
shift $((OPTIND - 1))

if ! command -v aria2c >/dev/null 2>&1; then
  echo "Error: aria2c not found. Install it first (brew install aria2 on macOS)." >&2
  exit 127
fi

if [ "$#" -lt 1 ]; then
  echo "Usage: $0 [--sane] [-o output] <url> [more_urls...]"
  exit 1
fi

# Detect max cap for --max-connection-per-server (usually 16)
detect_conn_cap() {
  local cap
  cap="$(aria2c -h 2>/dev/null | awk '
    /--max-connection-per-server=NUM/ {seen=1; next}
    seen && /Possible Values:/ {gsub(/[^0-9-]/,""); split($0,a,"-"); print a[2]; exit}
  ')"
  [[ "$cap" =~ ^[0-9]+$ ]] && echo "$cap" || echo 16
}
ARIA_CONN_CAP="$(detect_conn_cap)"

# Profile defaults
if [[ "$PROFILE" == "aggressive" ]]; then
  ARIA_CONN="${ARIA_CONN:-32}"
  ARIA_SPLIT="${ARIA_SPLIT:-32}"
  ARIA_CHUNK="${ARIA_CHUNK:-4M}"
  ARIA_CACHE="${ARIA_CACHE:-512M}"
else
  ARIA_CONN="${ARIA_CONN:-16}"
  ARIA_SPLIT="${ARIA_SPLIT:-16}"
  ARIA_CHUNK="${ARIA_CHUNK:-2M}"
  ARIA_CACHE="${ARIA_CACHE:-256M}"
fi
ARIA_TRIES="${ARIA_TRIES:-0}"
ARIA_WAIT="${ARIA_WAIT:-5}"

# Clamp connections
if (( ARIA_CONN > ARIA_CONN_CAP )); then
  echo "Note: clamping --max-connection-per-server from ${ARIA_CONN} to ${ARIA_CONN_CAP}" >&2
  ARIA_CONN="$ARIA_CONN_CAP"
fi

# Helper: check if aria2c supports an option
has_opt() {
  aria2c -h 2>/dev/null | grep -q -- "$1"
}

OPTS=(
  --continue=true
  --max-connection-per-server="${ARIA_CONN}"
  --split="${ARIA_SPLIT}"
  --min-split-size="${ARIA_CHUNK}"
  --piece-length="${ARIA_CHUNK}"
  --disk-cache="${ARIA_CACHE}"
  --file-allocation=none
  --auto-file-renaming=false
  --retry-wait="${ARIA_WAIT}"
  --max-tries="${ARIA_TRIES}"
  --conditional-get=true
  --uri-selector=inorder
  --console-log-level=warn
  --summary-interval=3
  --header="Accept-Encoding: identity"
  --reuse-uri=true
)

# Add only if supported
has_opt "--enable-mmap"    && OPTS+=( --enable-mmap=true )
has_opt "--async-dns"      && OPTS+=( --async-dns=true )

# Respect -o if one URL
if [ -n "$OUT_NAME" ] && [ "$#" -eq 1 ]; then
  OPTS+=( -o "$OUT_NAME" )
fi

aria2c "${OPTS[@]}" "$@"