#!/bin/bash

shellfu import pretty

#
# grep for (some) INIs
#
# inigrep is designed to read a particular simplistic dialect of
# INI configuration files.  In a sense, it can be considered as
# a "grep for INIs", in that rather than parsing the file into
# a typed memory structure for later access, it passes file each
# time a query is done, and spits out relevant parts; treating
# everything as text.  Hence, it's not intended as replacement
# for a full-blown configuration system but rather a quick & dirty
# "swiss axe" for quick & dirty scripts.
#
# That's not to say that you cannot do things nicely; but don't
# count on speed -- well since you're using bash you obviously
# don't -- and compliance -- simple things are simple, but there
# are a bit unusual pitfalls.
#
#
# The format by examples
# ----------------------
#
# The most basic example understood by inigrep is identical
# to most INI formats:
#
#     # Let's call this simple.ini
#
#     [foo]
#         bar = baz
#         qux = quux
#
#     [corge]
#         grault = graply
#
# Structure here is obvious: two sections named `foo` and `corge`,
# the first one has two key/value pairs and the other has one pair.
#
# Getting values from this file is trivial:
#
#     inigrep foo.bar simple.ini
#     inigrep foo.qux simple.ini
#     inigrep corge.grault simple.ini
#
# would list `baz`, `quux` and `graply`.
#
# This is where 80% of use cases are covered.
#
#
# Multi-line
# ----------
#
# Multi-line values are rather unusual but very simple:
#
#     [lipsum]
#
#         latin = Lorem ipsum dolor sit amet, consectetur adipiscing
#         latin = elit, sed do eiusmod tempor incididunt ut labore et
#         latin = dolore magna aliqua. Ut enim ad minim veniam, quis
#         latin = ...
#
#         english = [32] But I must explain to you how all this mistaken
#         english = idea of denouncing of a pleasure and praising pain
#         english = was born and I will give you a complete account of
#         english = ...
#
# This file can be read as:
#
#     inigrep lipsum.latin lipsum.ini
#     inigrep lipsum.english lipsum.ini
#
#
# Exploration
# -----------
#
# Other than basic value retrieval, inigrep allows you to look around
# first. For example, to list all keypaths available in a file:
#
#     inigrep -P simple.ini
#
# In case of simple.ini, this would print:
#
#     foo.bar
#     foo.qux
#     corge.grault
#
# Similarly:
#
#     inigrep -S simple.ini
#
# would list just the section names:
#
#     foo
#     corge
#
# and
#
#     inigrep -K foo simple.ini
#
# would list all keys from section 'foo'
#
#     bar
#     qux
#


_inigrep__fltcmt() {
    #
    # Just strip comments
    #
    perl -ne '
        chomp;
        next if m/^[[:space:]]*[#;]/;
        s/  *#.*//;
        s/  *;.*//;
        print "$_\n" if $_;
    '
}


_inigrep__fltkey() {
    #
    # Filter values from `key = value pairs`
    #
    # In listing mode, prints *key names* instead
    #
    local line      # every line
    local key       # key name part
    local value     # name part
    while IFS= read -r line;                        # '  key  =  val  '
    do
        line="${line##*([[:space:]])}"              # line='key  =  val  '
        key="${line%%*([[:space:]])=*}"             # key='key'
        value="${line##$key*([[:space:]])=}"        # value='  val  '
        $StrictMode || value="${value##*([[:space:]])}" # value='val'
        test "$key" = "$WantedKey" || continue
        $ListingMode || echos "$value"
        $ListingMode && echos "$line"
    done
}


_inigrep__fltsct() {
    #
    # Filter out only the wanted section body
    #
    # In listing mode prints also section name
    #
    local sct_ok=false  # is this the section we want?
    local sct_name      # wanted section name
    local line          # current line
    while IFS= read -r line;
    do
        if [[ $line =~ ^[[:space:]]*\[[^]]*\].* ]];     # IOW: 'spaces[name]anything'
        then
            # hack out only the name between '[' and ']'
            sct_name=$line
            sct_name=${sct_name##*([[:space:]])[}   # drop leading space
            sct_name=${sct_name%%]*}                # and trailing anything
            if test "$sct_name" == "$WantedSection";
            then
                sct_ok=true;                            # our section
                $ListingMode && echos "[$sct_name]";    # inform lister
            else
                sct_ok=false
            fi
            continue
        else
            $sct_ok || continue
            $StrictMode || line="${line##*([[:space:]])}"
            echos "$line"
        fi
    done
}


_inigrep__fltlst() {
    #
    # Filter only section/keys/path names from the stream
    #
    local line=""           # current line
    local key="__NOKEY__"   # current key
    local sct="__NOSCT__"   # current section
    while read -r line;
    do
        case "$line" in
            \[*\]) sct=${line#[}; sct=${sct%]}; key=__NOKEY__   ;;
            *=*)   key="${line%%*([[:space:]])=*}" ;;   # key='key'
            *)     continue ;;                          # whatever
        esac
        case "$Engine:$sct:$key" in
            lspth:__NOSCT__:*)         echos "$sct.$key" ;;
            lspth:*:__NOKEY__)         continue          ;;
            lspth:*:*)                 echos "$sct.$key" ;;
            lssct:__NOSCT__:*)         echos "$sct"      ;;
            lssct:*:__NOKEY__)         echos "$sct"      ;;
            lssct:*:*)                 continue          ;;
            lskey:__NOSCT__:__NOKEY__) continue          ;;
            lskey:__NOSCT__:*)         echos "$key"      ;;
            lskey:*:__NOKEY__)         continue          ;;
            lskey:*:*)                 echos "$key"      ;;
        esac
    done
}


_inigrep__query() {
    #
    # Query INI stream composed of files at $@ or stdin
    #
    # Compose filter pipe of potential parts and run it.
    #
    local pipe=""               # filter pipe
    local ListingMode=false     # listing mode on?
    local StrictMode=false      # strict mode on?
    local ifile                 # current input file
    local restore_shopt         # shopt backup (executable code)
    case $Engine in
        raw) StrictMode=true ;;
        ls*) ListingMode=true ;;
    esac
    # which will come first? prefix all and strip the first prefix
    #
    $StrictMode                 || pipe+=" | _inigrep__fltcmt"
    test -n "$WantedSection"    && pipe+=" | _inigrep__fltsct"
    test -n "$WantedKey"        && pipe+=" | _inigrep__fltkey"
    $ListingMode                && pipe+=" | _inigrep__fltlst"
    $StrictMode                 || pipe+=" | grep ."
    pipe="${pipe# | }"
    test -z "$pipe" && pipe="cat"   # possible with raw mode and dot wildcard
    debug -v pipe
    # pray and run
    #
    restore_shopt=$(shopt -p extglob)
    shopt -s extglob
    for ifile in "$@";
    do
        case "$ifile" in
            -) eval "$pipe" ;;
            *) <"$ifile" eval "$pipe" ;;
        esac
    done
    $restore_shopt
}

_inigrep__validate_ks() {
    #
    # Check $WantedSection ans $WantedKey for invalid chars and warn
    #
    case $WantedKey in
        *\\*) warn "invalid char '\\' in key name: $WantedKey"; return 1 ;;
        *[*)  warn "invalid char '[' in key name: $WantedKey"; return 1 ;;
        *=*)  warn "invalid char '=' in key name: $WantedKey"; return 1 ;;
    esac
    case $WantedSection in
        *]*)  warn "invalid char ']' in section name: $WantedSection"; return 1 ;;
    esac
}

inigrep() {
    #
    # Query INI file(s) for data
    #
    # Usage:
    #
    #     inigrep [-1] [section].[key] [file]...
    #     inigrep [-1] -e|--basic [section].[key] [file]...
    #     inigrep [-1] -r|--raw [section].[key] [file]...
    #     inigrep [-1] -K|--lskey section [file]...
    #     inigrep [-1] -S|--lssct [file]...
    #     inigrep [-1] -P|--lspth [file]...
    #
    # First form implies the basic engine.
    #
    # Option *-r* switches to raw mode, in which comments,
    # empty lines and whitespace are all preserved in applicable
    # contexts.
    #
    # Key *keypath* consists of section name and key name delimited
    # by dot.  Note that keypath may contain dots but key may not.
    #
    # If *file* is not given or is a single dash, standard input
    # is read.  Note that standard input is not duplicated in case
    # of multiple dashes.
    #
    # If suitable key is found at multiple lines, all values
    # are printed, which allows for creating multi-line values.
    # Providing *-1* argument, however, always prints only one
    # line.
    #
    # Options -K, -S and -P can be used for inspecting file structure;
    # -K needs an argument of section name and will list all keys from
    # that section.  -S will list all sections and -P will list all
    # existing keypaths.
    #
    #
    # #### Examples ####
    #
    # Having INI file such as
    #
    #     [foo]
    #     bar=baz
    #     quux=qux
    #     quux=qux2
    #     quux=qux3
    #
    #  *  `inigrep foo.bar ./file.ini` gives "bar".
    #  *  `inigrep foo.quux ./file.ini` gives three lines "qux", "qux2"
    #     and "qux3".
    #  *  `inigrep -P ./file.ini` gives two lines "foo.bar" and "foo.quux".
    #  *  `inigrep -K foo ./file.ini` gives two lines "bar" and "quux".
    #  *  `inigrep -S ./file.ini` gives "foo".
    #
    local kpath=""              # desired key path
    local one_line=false        # limit to single line
    local Engine=ini            # engine: ini,raw,lspth,lssct,lskey
    local WantedSection=""      # desired section name (in case of listing)
    local WantedKey=""          # desired key name
    while true; do case $1 in
        -1|--one-line)  one_line=true;              shift        ;;
        -e|--basic)     Engine=ini;    kpath="$2";  shift; break ;;
        -r|--raw)       Engine=raw;    kpath="$2";  shift; break ;;
        -K|--lskey)     Engine=lskey;  kpath="$2."; shift; break ;;
        -P|--lspth)     Engine=lspth;  kpath=".";          break ;;
        -S|--lssct)     Engine=lssct;  kpath=".";          break ;;
        *)                                                 break ;;
    esac done
    test -n "$kpath" || kpath="$1" && shift
    test -z "$*" && set -- -
    debug -v one_line Engine kpath
    debug "\$*='$*'"
    WantedKey="${kpath##*.}"
    WantedSection="${kpath%.$WantedKey}"
    _inigrep__validate_ks || return 2
    debug -v WantedKey WantedSection
    if $one_line;
    then
        _inigrep__query "$@" | head -1
    else
        _inigrep__query "$@"
    fi
}

#shellfu module-version=__MKIT_PROJ_VERSION__