zsh-autosuggestions/src/strategies/match_prev_cmd.zsh

#--------------------------------------------------------------------#
# Match Previous Command Suggestion Strategy                         #
#--------------------------------------------------------------------#
# Suggests the most recent history item that matches the given
# prefix and whose preceding history item also matches the most
# recently executed command.
#
# For example, suppose your history has the following entries:
#   - pwd
#   - ls foo
#   - ls bar
#   - pwd
#
# Given the history list above, when you type 'ls', the suggestion
# will be 'ls foo' rather than 'ls bar' because your most recently
# executed command (pwd) was previously followed by 'ls foo'.
#
# Note that this strategy won't work as expected with ZSH options that don't
# preserve the history order such as `HIST_IGNORE_ALL_DUPS` or
# `HIST_EXPIRE_DUPS_FIRST`.

_zsh_autosuggest_strategy_match_prev_cmd() {
	# Reset options to defaults and enable LOCAL_OPTIONS
	emulate -L zsh

	# Enable globbing flags so that we can use (#m)
	setopt EXTENDED_GLOB

	# TODO: Use (b) flag when we can drop support for zsh older than v5.0.8
	local prefix="${1//(#m)[\\*?[\]<>()|^~#]/\\$MATCH}"

	# Get all history event numbers that correspond to history
	# entries that match pattern $prefix*
	local history_match_keys
	history_match_keys=(${(k)history[(R)$prefix*]})

	# By default we use the first history number (most recent history entry)
	local histkey="${history_match_keys[1]}"

	# Get the previously executed command
	local prev_cmd="$(_zsh_autosuggest_escape_command "${history[$((HISTCMD-1))]}")"

	# Iterate up to the first 200 history event numbers that match $prefix
	for key in "${(@)history_match_keys[1,200]}"; do
		# Stop if we ran out of history
		[[ $key -gt 1 ]] || break

		# See if the history entry preceding the suggestion matches the
		# previous command, and use it if it does
		if [[ "${history[$((key - 1))]}" == "$prev_cmd" ]]; then
			histkey="$key"
			break
		fi
	done

	# Give back the matched history entry
	typeset -g suggestion="$history[$histkey]"
}