Zsh Completion System

# Load and initialize
autoload -Uz compinit
compinit

# With caching (faster startup)
autoload -Uz compinit
if [[ -n ${ZDOTDIR:-$HOME}/.zcompdump(#qN.mh+24) ]]; then
  compinit
else
  compinit -C                            # skip security check (faster)
fi

# Menu selection (navigate with arrows)
zstyle ':completion:*' menu select

# Case-insensitive matching
zstyle ':completion:*' matcher-list 'm:{a-zA-Z}={A-Za-z}'

# Partial word completion
zstyle ':completion:*' matcher-list '' \
  'm:{a-zA-Z}={A-Za-z}' \
  'r:|[._-]=* r:|=*' \
  'l:|=* r:|=*'

# Group completions by category
zstyle ':completion:*' group-name ''
zstyle ':completion:*:descriptions' format '%F{green}-- %d --%f'
zstyle ':completion:*:warnings' format '%F{red}-- no matches --%f'

# Colors in completion menu
zstyle ':completion:*' list-colors ${(s.:.)LS_COLORS}

# Use caching
zstyle ':completion:*' use-cache yes
zstyle ':completion:*' cache-path "$HOME/.zsh/cache"

# Simple word list completion
_mycommand() {
  local -a options
  options=(
    'start:Start the service'
    'stop:Stop the service'
    'restart:Restart the service'
    'status:Show status'
  )
  _describe 'command' options
}
compdef _mycommand mycommand

# File-type restricted completion
zstyle ':completion:*:*:nvim:*' file-patterns \
  '*.{lua,py,sh,adoc,md,yml,yaml,json,toml}:source-files:Source Files' \
  '*:all-files:All Files'

# SSH host completion from config
zstyle ':completion:*:ssh:*' hosts $(
  awk '/^Host / && !/\*/ {print $2}' ~/.ssh/config 2>/dev/null
)

# Kill process completion with menu
zstyle ':completion:*:*:kill:*' menu yes select
zstyle ':completion:*:kill:*' force-list always
zstyle ':completion:*:*:kill:*' command 'ps -u $USER -o pid,%cpu,tty,cputime,cmd'

# Which completion function handles a command
echo ${(k)_comps[git]}                   # show function name

# Rebuild completion cache
rm -f ~/.zcompdump && compinit

# Trace completion
# Ctrl+x h                              # show completion context
# Ctrl+x ?                              # show completion info

# List all completions
print -l ${(k)_comps} | sort            # all registered completions

# Add completion directory
fpath=(~/.zsh/completions $fpath)

# Tab             complete
# Shift-Tab       reverse cycle (with menu select)
# Ctrl-x Ctrl-f   file completion anywhere
# Ctrl-x Ctrl-a   expand alias

# Path completion
cd /u/l/b<Tab>                           # → /usr/local/bin

# Variable completion
echo $PA<Tab>                            # → $PATH

# Command option completion
git log --<Tab>                          # shows all --options

# Process completion
kill <Tab>                               # shows process list