#!/usr/bin/env sh
#MISE description="Link the agent config for your harnesses and version control"
#MISE alias=["setup:agent", "su:agents", "su:agent"]

set -e

CONFIG=".agents/config.yml"
GENERATED="# Generated by mise run setup:agents. Edit the source in .agents/agents instead."
HARNESSES="claude codex opencode"
PROFILES="git gitbutler jujutsu"
overwrite=""

for arg in "$@"; do
  case "$arg" in
  --overwrite) overwrite="1" ;;
  *)
    echo "unknown argument: $arg" >&2
    exit 1
    ;;
  esac
done

read_config() {
  [ -f "$CONFIG" ] || return 0
  sed -n "s/^$1:[[:space:]]*//p" "$CONFIG" | head -n 1
}

read_config_list() {
  [ -f "$CONFIG" ] || return 0

  awk -v key="$1:" '
    $0 == key { inside = 1; next }
    /^[^[:space:]-]/ { inside = 0 }
    inside && /^[[:space:]]*-[[:space:]]*/ {
      sub(/^[[:space:]]*-[[:space:]]*/, "")
      print
    }
  ' "$CONFIG" | tr '\n' ' '
}

guess_vcs() {
  if [ -d ".jj" ]; then
    echo "jujutsu"
  elif [ -d ".git/gitbutler" ]; then
    echo "gitbutler"
  else
    echo "git"
  fi
}

choose() {
  limit="$1"
  header="$2"
  default="$3"
  shift 3

  if [ ! -t 0 ]; then
    echo "$default"
    return 0
  fi

  gum choose --header "$header" --selected "$(echo "$default" | tr ' ' ',')" "$limit" "$@" | tr '\n' ' '
}

choose_many() {
  choose "--no-limit" "$@"
}

choose_one() {
  choose "--limit=1" "$@"
}

up_to_root() {
  prefix=""
  dir=$(dirname "$1")

  while [ "$dir" != "." ]; do
    prefix="../$prefix"
    dir=$(dirname "$dir")
  done

  printf '%s' "$prefix"
}

link() {
  source="$1"
  path="$2"

  if [ -e "$path" ] && [ ! -L "$path" ]; then
    echo "refusing to replace $path: it is not a symlink" >&2
    exit 1
  fi

  mkdir -p "$(dirname "$path")"
  rm -f "$path"
  ln -s "$(up_to_root "$path")$source" "$path"
}

prune() {
  [ -d "$1" ] || return 0

  find "$1" -type l | while IFS= read -r path; do
    case "$(readlink "$path")" in
    *".agents/"*) rm "$path" ;;
    esac
  done

  find "$1" -type f -name "*.toml" | while IFS= read -r path; do
    if [ "$(head -n 1 "$path")" = "$GENERATED" ]; then
      rm "$path"
    fi
  done

  find "$1" -mindepth 1 -type d -empty -delete
  rmdir "$1" 2>/dev/null || true
}

prune_all() {
  prune ".claude"
  prune ".codex"
}

link_skills() {
  for path in .agents/skills/*/SKILL.md; do
    link "$path" "$1/skills/$(basename "$(dirname "$path")")/SKILL.md"
  done
}

setup_claude() {
  link ".agents/AGENTS.md" ".claude/CLAUDE.md"

  for path in .agents/agents/*.md; do
    link "$path" ".claude/agents/$(basename "$path")"
  done

  link_skills ".claude"
}

frontmatter() {
  awk -v key="$2" '
    NR == 1 && $0 == "---" { inside = 1; next }
    inside && $0 == "---" { exit }
    inside && index($0, key ": ") == 1 { print substr($0, length(key) + 3) }
  ' "$1"
}

body() {
  awk '
    NR == 1 && $0 == "---" { inside = 1; next }
    inside && $0 == "---" { inside = 0; started = 1; next }
    inside { next }
    started && !seen && $0 == "" { next }
    { seen = 1; print }
  ' "$1"
}

toml_string() {
  printf '"%s"' "$(printf '%s' "$1" | sed -e 's/\\/\\\\/g' -e 's/"/\\"/g')"
}

# Codex reads agents as TOML, so a symlink will not do. Build one from the
# markdown instead, and mark it so prune knows it can remove it.
agent_to_toml() {
  source="$1"
  path="$2"

  if body "$source" | grep -q "'''"; then
    echo "refusing to convert $source: its body holds ''' and cannot sit in a TOML literal string" >&2
    exit 1
  fi

  if [ -e "$path" ] && [ "$(head -n 1 "$path")" != "$GENERATED" ]; then
    echo "refusing to replace $path: setup:agents did not write it" >&2
    exit 1
  fi

  mkdir -p "$(dirname "$path")"

  {
    echo "$GENERATED"
    echo "name = $(toml_string "$(frontmatter "$source" name)")"
    echo "description = $(toml_string "$(frontmatter "$source" description)")"
    echo "developer_instructions = '''"
    body "$source"
    echo "'''"
  } >"$path"
}

setup_codex() {
  for path in .agents/agents/*.md; do
    agent_to_toml "$path" ".codex/agents/$(basename "$path" .md).toml"
  done

  link_skills ".codex"
}

setup_opencode() {
  echo "opencode reads .agents/skills and AGENTS.md itself, nothing to link"
}

harnesses=$(read_config_list "harnesses" | xargs)
vcs=$(read_config "vcs")

if [ -z "$harnesses" ] || [ -z "$vcs" ] || [ -n "$overwrite" ]; then
  # shellcheck disable=SC2086
  harnesses=$(choose_many "Which harnesses do you use? Space toggles, enter confirms." "${harnesses:-claude}" $HARNESSES)
  # shellcheck disable=SC2086
  vcs=$(choose_one "Which version control do you use?" "${vcs:-$(guess_vcs)}" $PROFILES)

  harnesses=$(echo "$harnesses" | xargs)
  vcs=$(echo "$vcs" | xargs)

  {
    echo "# Written by mise run setup:agents. Change it with --overwrite."
    echo "harnesses:"

    for harness in $harnesses; do
      echo "  - $harness"
    done

    echo "vcs: $vcs"
  } >"$CONFIG"
fi

if [ ! -f ".agents/profiles/vcs/$vcs.md" ]; then
  echo "no profile for $vcs. Pick one of: $PROFILES" >&2
  exit 1
fi

link ".agents/profiles/vcs/$vcs.md" ".agents/vcs.md"
prune_all

for harness in $harnesses; do
  case " $HARNESSES " in
  *" $harness "*) "setup_$harness" ;;
  *)
    echo "no harness named $harness. Pick from: $HARNESSES" >&2
    exit 1
    ;;
  esac
done

echo "set up $harnesses against the $vcs profile"