#!/usr/bin/env bash
set -euo pipefail

repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/../../../../" && pwd)"
repo_skills_dir="$repo_root/.github/skills"
global_skills_dir="${HOME}/.copilot/skills"

source_input="${1:-}"
scope_input="${2:-}"
name_input="${3:-}"

prompt() {
  local message="$1"
  local default_value="${2:-}"
  local reply
  if [[ -n "$default_value" ]]; then
    read -r -p "${message} [${default_value}]: " reply
    printf '%s\n' "${reply:-$default_value}"
  else
    read -r -p "${message}: " reply
    printf '%s\n' "$reply"
  fi
}

normalize_name() {
  tr '[:upper:] ' '[:lower:]-' | tr -cd 'a-z0-9-'
}

rewrite_github_blob_url() {
  local url="$1"
  if [[ "$url" =~ ^https://github\.com/([^/]+)/([^/]+)/blob/([^/]+)/(.*)$ ]]; then
    printf 'https://raw.githubusercontent.com/%s/%s/%s/%s\n' "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}" "${BASH_REMATCH[3]}" "${BASH_REMATCH[4]}"
  else
    printf '%s\n' "$url"
  fi
}

parse_github_blob_url() {
  local url="$1"
  if [[ "$url" =~ ^https://github\.com/([^/]+)/([^/]+)/blob/([^/]+)/(.*)$ ]]; then
    printf '%s\t%s\t%s\t%s\n' "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}" "${BASH_REMATCH[3]}" "${BASH_REMATCH[4]}"
    return 0
  fi

  return 1
}

extract_skill_name() {
  local file="$1"
  sed -n 's/^name:[[:space:]]*//p' "$file" | head -n 1
}

download_source() {
  local url="$1"
  local out="$2"
  curl -fsSL "$url" -o "$out"
}

list_github_contents() {
  local owner="$1"
  local repo="$2"
  local ref="$3"
  local path="$4"

  curl -fsSL -H 'Accept: application/vnd.github+json' \
    "https://api.github.com/repos/${owner}/${repo}/contents/${path}?ref=${ref}" | \
    python3 -c $'import json,sys\ndata = json.load(sys.stdin)\nitems = data if isinstance(data, list) else [data]\nfor item in items:\n    print("%s\\t%s\\t%s" % (item.get("type", ""), item.get("path", ""), item.get("download_url", "")))'
}

download_github_contents() {
  local owner="$1"
  local repo="$2"
  local ref="$3"
  local path="$4"
  local target_root="$5"

  while IFS=$'\t' read -r item_type item_path download_url; do
    [[ -z "$item_type" ]] && continue

    local relative_path="${item_path#${path}/}"
    local destination_path="$target_root/$relative_path"

    case "$item_type" in
      dir)
        download_github_contents "$owner" "$repo" "$ref" "$item_path" "$target_root"
        ;;
      file)
        mkdir -p "$(dirname "$destination_path")"
        download_source "$download_url" "$destination_path"
        ;;
      *)
        printf 'Skipping unsupported GitHub content type: %s (%s)\n' "$item_type" "$item_path" >&2
        ;;
    esac
  done < <(list_github_contents "$owner" "$repo" "$ref" "$path")
}

copy_skill_dir() {
  local source_dir="$1"
  local target_dir="$2"
  local include_supporting_files="$3"

  mkdir -p "$target_dir"
  if [[ "$include_supporting_files" == "yes" ]]; then
    cp -R "$source_dir"/. "$target_dir"/
  else
    cp "$source_dir/SKILL.md" "$target_dir/SKILL.md"
  fi
}

if [[ -z "$source_input" ]]; then
  source_input="$(prompt "Source path, directory, or GitHub SKILL.md URL")"
fi

if [[ -z "$scope_input" ]]; then
  scope_input="$(prompt "Target scope (repo/global)" "repo")"
fi

if [[ "$scope_input" != "repo" && "$scope_input" != "global" ]]; then
  printf 'Invalid scope: %s\n' "$scope_input" >&2
  exit 1
fi

tmpdir="$(mktemp -d)"
trap 'rm -rf "$tmpdir"' EXIT

staging_dir="$tmpdir/staging"
mkdir -p "$staging_dir"

source_kind=""
source_path="$source_input"

if [[ "$source_input" =~ ^https?:// ]]; then
  if github_blob_parts="$(parse_github_blob_url "$source_input")"; then
    source_kind="github-blob-url"
    IFS=$'\t' read -r github_owner github_repo github_ref github_path <<<"$github_blob_parts"
    github_skill_dir="$(dirname "$github_path")"
    download_github_contents "$github_owner" "$github_repo" "$github_ref" "$github_skill_dir" "$staging_dir"
  else
    source_kind="url"
    source_path="$(rewrite_github_blob_url "$source_input")"
    download_source "$source_path" "$staging_dir/SKILL.md"
  fi
elif [[ -d "$source_input" ]]; then
  source_kind="directory"
  skill_file="$source_input/SKILL.md"
  if [[ ! -f "$skill_file" ]]; then
    printf 'Missing SKILL.md in source directory: %s\n' "$source_input" >&2
    exit 1
  fi
  include_supporting_files="$(prompt "Copy supporting files too? (yes/no)" "no")"
  copy_skill_dir "$source_input" "$staging_dir" "$include_supporting_files"
elif [[ -f "$source_input" ]]; then
  source_kind="file"
  cp "$source_input" "$staging_dir/SKILL.md"
else
  printf 'Source not found: %s\n' "$source_input" >&2
  exit 1
fi

if [[ ! -f "$staging_dir/SKILL.md" ]]; then
  printf 'No SKILL.md was staged from %s source.\n' "$source_kind" >&2
  exit 1
fi

inferred_name="$(extract_skill_name "$staging_dir/SKILL.md")"
if [[ -z "$name_input" ]]; then
  name_input="$(prompt "Skill name" "${inferred_name:-skill}")"
fi
skill_name="$(printf '%s' "$name_input" | normalize_name)"

if [[ -z "$skill_name" ]]; then
  printf 'Skill name cannot be empty.\n' >&2
  exit 1
fi

if [[ "$scope_input" == "repo" ]]; then
  target_base="$repo_skills_dir"
else
  target_base="$global_skills_dir"
fi

target_dir="$target_base/$skill_name"
if [[ -e "$target_dir" ]]; then
  overwrite="$(prompt "Target exists at ${target_dir}. Overwrite? (yes/no)" "no")"
  if [[ "$overwrite" != "yes" ]]; then
    printf 'Aborted.\n'
    exit 1
  fi
  rm -rf "$target_dir"
fi

mkdir -p "$target_dir"
cp -R "$staging_dir"/. "$target_dir"/

if [[ ! -f "$target_dir/SKILL.md" ]]; then
  printf 'Install failed: %s/SKILL.md missing after copy.\n' "$target_dir" >&2
  exit 1
fi

echo "<$source_input>" >"$target_dir/source.md"

printf 'Installed %s skill to %s\n' "$skill_name" "$target_dir"