#!/usr/bin/env bash

set -u
set -o pipefail

ROOT_DIR=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)
TMP_DIR=$(mktemp -d "${TMPDIR:-/tmp}/cowsay-tour.XXXXXX")
trap 'rm -rf "$TMP_DIR"' EXIT

AUTO_RUN=0
COUNTDOWN=10
STOP_TOUR=0
COMPILER=""

usage() {
  cat <<'EOF'
Usage:
  ./tour_programmes.sh
  ./tour_programmes.sh --auto

Options:
  --auto      starts immediately without waiting
  -h, --help  shows this help
EOF
}

while (($# > 0)); do
  case "$1" in
  --auto)
    AUTO_RUN=1
    ;;
  -h | --help)
    usage
    exit 0
    ;;
  *)
    printf 'Unknown option: %s\n\n' "$1" >&2
    usage >&2
    exit 1
    ;;
  esac
  shift
done

hr() {
  printf '\n============================================================\n'
}

show_intro() {
  hr
  printf 'Quick cowsay program tour\n'
  if ((AUTO_RUN == 1)); then
    printf 'Auto mode: demos start immediately.\n'
  else
    printf 'The first demo starts after %d seconds.\n' "$COUNTDOWN"
    printf 'After each demo, the tour waits %d seconds before the next one.\n' "$COUNTDOWN"
    printf 'Press Enter to continue faster, or type n then Enter to stop.\n'
  fi
}

need_commands() {
  local missing=0
  local cmd

  for cmd in "$@"; do
    if ! command -v "$cmd" >/dev/null 2>&1; then
      printf 'Missing dependency: %s\n' "$cmd" >&2
      missing=1
    fi
  done

  return "$missing"
}

detect_compiler() {
  if [[ -n "$COMPILER" ]]; then
    return 0
  fi

  local candidate
  for candidate in cc clang gcc; do
    if command -v "$candidate" >/dev/null 2>&1; then
      COMPILER="$candidate"
      return 0
    fi
  done

  printf 'No C compiler found.\n' >&2
  return 1
}

compile_c() {
  local source="$1"
  local output="$2"

  detect_compiler || return 1
  "$COMPILER" -std=c99 -Wall -Wextra -O2 -D_DEFAULT_SOURCE "$source" -o "$output"
}

run_command() {
  "$@"
}

run_command_with_input() {
  local input="$1"
  shift
  printf '%s' "$input" | "$@"
}

announce_demo() {
  local name="$1"
  local description="$2"

  hr
  printf '%s: %s\n' "$name" "$description"
}

drain_stdin() {
  if [[ ! -t 0 ]]; then
    return 0
  fi

  while IFS= read -r -t 0; do
    :
  done
}

timed_continue() {
  local prompt="$1"

  if ((AUTO_RUN == 1)) || [[ ! -t 0 ]]; then
    printf 'Starting...\n'
    return 0
  fi

  drain_stdin
  printf '%s' "$prompt"

  local answer=""
  if IFS= read -r -t "$COUNTDOWN" answer; then
    printf '\n'
    case "${answer,,}" in
    n)
      STOP_TOUR=1
      return 1
      ;;
    *)
      return 0
      ;;
    esac
  fi

  printf '\n'
  return 0
}

run_demo() {
  local name="$1"
  local function_name="$2"

  "$function_name"
  local status=$?

  if ((status != 0)); then
    printf '%s: failed (%d)\n' "$name" "$status" >&2
  fi
}

demo_cow_kindergarten() {
  need_commands cowsay || return 1
  run_command bash "$ROOT_DIR/src/bash_scripts/cow_kindergarten.sh"
}

demo_cow_primaryschool() {
  need_commands cowsay || return 1
  run_command bash "$ROOT_DIR/src/bash_scripts/cow_primaryschool.sh" 3
}

demo_cow_highschool() {
  need_commands cowsay || return 1
  run_command bash "$ROOT_DIR/src/bash_scripts/cow_highschool.sh" 3
}

demo_cow_college() {
  need_commands cowsay || return 1
  run_command bash "$ROOT_DIR/src/bash_scripts/cow_college.sh" 5
}

demo_cow_university() {
  need_commands cowsay || return 1
  run_command bash "$ROOT_DIR/src/bash_scripts/cow_university.sh" 12
}

demo_smart_cow() {
  need_commands cowsay bc || return 1
  run_command bash "$ROOT_DIR/src/bash_scripts/smart_cow.sh" '4+13'
}

demo_crazy_cow() {
  need_commands cowsay || return 1
  run_command_with_input $'5\n' bash "$ROOT_DIR/src/bash_scripts/crazy_cow.sh"
}

demo_newcow() {
  local bin="$TMP_DIR/newcow"
  compile_c "$ROOT_DIR/src/C/newcow.c" "$bin" || return 1
  run_command "$bin" -e "^^"
}

demo_newcowt() {
  local bin="$TMP_DIR/newcowT"
  compile_c "$ROOT_DIR/src/C/newcows/newcowT.c" "$bin" || return 1
  run_command "$bin" -T "U"
}

demo_newcowp() {
  local bin="$TMP_DIR/newcowp"
  compile_c "$ROOT_DIR/src/C/newcows/newcowp.c" "$bin" || return 1
  run_command "$bin" -p "Hello"
}

demo_newcow2() {
  local bin="$TMP_DIR/newcow2"
  compile_c "$ROOT_DIR/src/C/newcow2.c" "$bin" || return 1
  run_command "$bin" blink
}

demo_reading_cow() {
  local bin="$TMP_DIR/reading_cow"
  local sample="$TMP_DIR/reading_demo.txt"

  compile_c "$ROOT_DIR/src/C/reading_cow.c" "$bin" || return 1
  printf 'Hello.\nI read.\n' >"$sample"
  run_command "$bin" --i 0.10 "$sample"
}

demo_tamagoshi_cow() {
  local bin="$TMP_DIR/tamagoshi_cow"

  if ((AUTO_RUN == 1)) || [[ ! -t 0 ]]; then
    printf 'Tamagoshi skipped in auto mode.\n'
    return 0
  fi

  compile_c "$ROOT_DIR/src/C/tamagoshi_cow.c" "$bin" || return 1
  run_command "$bin"
}

visit_programs() {
  local -a names=(
    'cow_kindergarten.sh'
    'cow_primaryschool.sh'
    'cow_highschool.sh'
    'cow_college.sh'
    'cow_university.sh'
    'smart_cow.sh'
    'crazy_cow.sh'
    'newcow.c'
    'newcowT.c'
    'newcowp.c'
    'newcow2.c'
    'reading_cow.c'
    'tamagoshi_cow.c'
  )
  local -a descriptions=(
    'Counts from 1 to 10.'
    'Counts up to n.'
    'Shows square numbers.'
    'Shows Fibonacci.'
    'Shows prime numbers.'
    'Calculates an expression.'
    'Generates a weird sequence.'
    'Basic cow.'
    'Cow with a tongue option.'
    'Cow with a speech bubble.'
    'Compiles a .c file into .out.'
    'Animates the cow.'
    'The cow reads a file.'
    'Small cow game.'
  )
  local -a functions=(
    'demo_cow_kindergarten'
    'demo_cow_primaryschool'
    'demo_cow_highschool'
    'demo_cow_college'
    'demo_cow_university'
    'demo_smart_cow'
    'demo_crazy_cow'
    'demo_newcow'
    'demo_newcowt'
    'demo_newcowp'
    'demo_newcow2'
    'demo_reading_cow'
    'demo_tamagoshi_cow'
  )

  local total=${#names[@]}
  local i

  for ((i = 0; i < total; i++)); do
    announce_demo "${names[i]}" "${descriptions[i]}"

    if ((i == 0)); then
      timed_continue "Press Enter to start, type n then Enter to stop, auto-start in ${COUNTDOWN} seconds... " || return
    else
      timed_continue "Press Enter to start the next program, type n then Enter to stop, or wait ${COUNTDOWN} seconds... " || return
    fi

    run_demo "${names[i]}" "${functions[i]}"
    ((STOP_TOUR == 1)) && return
  done
}

show_outro() {
  hr
  if ((STOP_TOUR == 1)); then
    printf 'Tour stopped.\n'
  else
    printf 'End of tour.\n'
  fi
}

show_intro
visit_programs
show_outro