Peg grammar optimizer

optimizer.sh

#!/bin/bash

# Usage: optimizer.sh [-v] <file.peg>

set -e

dbg() {
    if [ "$VERBOSE" ]; then
        echo "$1" > /dev/stderr
    fi
}

read_rules() {
    while read -r NAME ASSIGN RULE; do
        if [ "$ASSIGN" = "<-" ]; then
            RULES["$NAME"]="$RULE"
            ORDER+=("$NAME")
        else
            echo "Error in normalization!"
            exit 1
        fi
    done
}

read_code() {
    PREFIX="$(sed '/[^ ]*\s*<-/,$d' "$1")"
    SUFFIX="$(sed -n '/%%/,$p' "$1")"
}

normalize() {
    sed '
        /^#/d;
        /^%%/,$d;
    ' "$1" | tr '\n' ' ' | sed '
        s/\([^ ]\+\)\s*<-\s*/\n\1 <- /g;
    ' | sed '
        s/\s*%\(header\|prefix\|auxil\|source\).*//;
        /^$/d;
    '
    echo
}

find_simple_rules() {
    for NAME in "${!RULES[@]}"; do
        if [[ "${RULES[$NAME]}" =~ [/] ]]; then
            continue
        fi
        if [[ "${RULES[$NAME]}" =~ \$[0-9] ]]; then
            continue
        fi
        SIMPLE+=("$NAME")
    done
}

inline_simple_rules() {
    local PATTERNS
    for RULE in "${SIMPLE[@]}"; do
        PATTERN="${RULES["$RULE"]//\\/\\\\}"
        PATTERN="${PATTERN//\|/\\\|}"
        PATTERNS+="s|\b$RULE\b|($PATTERN)|g;"
    done
    for NAME in "${!RULES[@]}"; do
        REPLACED="${RULES[$NAME]}"
        PREV=""
        while [ "$REPLACED" != "$PREV" ]; do
            PREV="$REPLACED"
            REPLACED="$(sed "$PATTERNS" <<<"$REPLACED")"
        done
        if [ "${RULES["$NAME"]}" != "$REPLACED" ]; then
            dbg "Replacing simple rules in $NAME:"
            dbg "- ${RULES["$NAME"]}"
            dbg "+ $REPLACED"
            RULES["$NAME"]="$REPLACED"
        fi
    done
    for RULE in "${SIMPLE[@]}"; do
        unset RULES["$RULE"]
    done
}

print_result() {
    echo "$PREFIX"
    echo
    for NAME in "${ORDER[@]}"; do
        if [ "${RULES["$NAME"]}" ]; then
            echo "$NAME <- ${RULES[$NAME]}"
        fi
    done
    echo
    echo "$SUFFIX"
}

main() {
    declare -A RULES=()
    declare -a SIMPLE=()
    declare -a ORDER=()

    if [ "$1" = "-v" ]; then
        VERBOSE="true"
        shift
    fi

    read_code "$1"
    read_rules < <(normalize "$1")
    find_simple_rules
    dbg "Simple rules: ${SIMPLE[*]}"
    inline_simple_rules
    print_result
}

main "$@"