#!/bin/bash

shellfu import exit

#
# Application debug mode
#
PRETTY_DEBUG=${PRETTY_DEBUG:-}

#
# Comma-separated list of module/function names to exclude from debuging
#
# For the sake of readability of your debug dumps, you can set this
# variable to comma-separated list of module or function names that
# you don't expect to get useful info from.
#
# If the caller has a qualified name (`modname__funcname()`, according
# to Shellfu naming scheme it's possible to use just module name here
# to mute all debug from that module (including internal functions).
# Otherwise, full function name should be listed.
#
PRETTY_DEBUG_EXCLUDE=${PRETTY_DEBUG_EXCLUDE:-}

#
# Application verbosity mode
#
PRETTY_VERBOSE=${PRETTY_VERBOSE:-}

#
# Name of pretty-printer module
#
# Friendly name of module used for decorating output.  For
# example, if the value is NAME, a _pretty_NAME module must
# exist and be importable.  Otherwise pretty will fall back
# to plain, which is also the default value.
#
PRETTY=${PRETTY:-plain}

#
# Usage display mode
#
# How to determine program name for purposes of usage messages.
#
# If empty, use basename of "$0".  Set to 'subcommand' to remove first
# dash (so that `path/to/foo-bar becomes `foo bar` which may make more
# sense in meta-command scenrarios).  Set to self=NAME to force NAME.
#
PRETTY_USAGE=${PRETTY_USAGE:-}


__shellfu_pretty__init() {
    #
    # Import proper submodule
    #
    if shellfu try_import "_pretty_${PRETTY}"; then
        shellfu import "_pretty_${PRETTY}"
        return 0
    else
        warn "falling back to _pretty_plain"
        PRETTY=plain
        shellfu import "_pretty_${PRETTY}"
    fi
}


##--------------------##
## PRINTING FRONT-END ##
##--------------------##

debug() {
    #
    # You already know what it does
    #
    # BTW, following are equivalent:
    #
    #     debug "var1=$var1" "var2=$var2" "result=$result"
    #     debug -v var1 var2 result
    #
    test "$PRETTY_DEBUG" == true || return 0
    _pretty__echo "$@"
}


debug_pipe() {
    #
    # Debug the whole pipe.
    #
    while IFS= read -r line; do
        debug "|$1: '$line'"
        echos "$line"
    done
}


die() {
    #
    # A fatal error
    #
    _pretty__echo -t
    _pretty__echo "$@"
    exit_error
}


echos() {
    #
    # Safer version of echo able to echo "-n"
    #
    # Traditional echo is broken in that it does not
    # distinguish between string to print and its own switches
    # (-e, -E or -n), leading to unexpected behavior.
    #
    # This echo version circumvents this by using printf.
    #
    printf -- '%s\n' "$@"
}


mkusage() {
    #
    # Echo out usage patterns and (by default) `exit 2`
    #
    #     mkusage [-w MSG] [-e STATUS] [-E] pattern [patern...]
    #
    # Each pattern is prefixed by "usage: " and a resolved
    # script/function name to produce traditional usage hint.
    # By default, will exit with status *EXIT_USAGE*, you
    # can use `-e STATUS` to specify other number. `-k` can be
    # used as shorthand for `-e 0` (e.g. if user asked for
    # the patterns)
    #
    # Use `-E` to prevent exiting; in that case, the status
    # that would be fed to `exit` will be used as exit status
    # of this function.
    #
    # Optionally, you can add -w MSG to add clarifying message
    # (presented as warning) to help user understand what is
    # wrong with arguments they have passed.  Alternatively,
    # -m SUBJ, -M SUBJ, -u SUBJ, and -U SUBJ are shorthands for
    # error messages describing missing positional argument (-m),
    # missing value to a parametrized argument (-M), unknown
    # argument (-u) or unknown command (-U).  Using these
    # shorthands you don't need  to provide whole message, but
    # only subject in question; rest of the message is provided
    # by pretty.sh.
    #
    # Use "--" to delimit end of arguments processed by mkusage.
    #
    # Recommended usage is to define usage() in your script and
    # use this in its body.  That way you only need to define
    # usage patterns once and skip to them from any place where
    # you detect incorrect usage.  Optionally, this usage()
    # function can pass first argument as -w for clarification
    # messages.
    #
    local es=$EXIT_USAGE    # our exit status
    local doexit=true       # should we exit?
    local cmsg              # clarification message
    while true; do case "$1" in
        -e) es="$2";        shift 2 || return 2 ;;
        -E) doexit=false;   shift ;;
        -k) es=$EXIT_OK;    shift ;;
        -w) cmsg="$2";      shift 2 || return 2 ;;
        -m) cmsg="no $2?";  shift 2 || return 2 ;;
        -M) cmsg="missing value for: $2";    shift 2 || return 2 ;;
        -u) cmsg="unknown argument: $2";     shift 2 || return 2 ;;
        -U) cmsg="unknown command: $2";      shift 2 || return 2 ;;
        --)                 shift; break ;;
        *)                  break ;;
    esac done
    _pretty__echo -u "$@";
    if test -n "$cmsg"; then
        test -n "$*" && echo >&2
        warn "bad usage: $cmsg"
    fi
    $doexit && exit "$es"
    return "$es"
}


mkhelp() {
    #
    # Echo out help text
    #
    #     mkhelp [-e STATUS] [-E] arg...
    #
    # By default, will exit with status *EXIT_OK*, you
    # can use `-e STATUS` to specify other number.
    #
    # Use `-E` to prevent exiting; in that case, the status
    # that would be fed to `exit` will be used as exit status
    # of this function.
    #
    # Use "--" to delimit end of arguments processed by mkhelp
    #
    local es=$EXIT_OK
    local doexit=true
    while true; do case "$1" in
        -e) es="$2";            shift 2 || return 2 ;;
        -E) doexit=false;       shift               ;;
        --)                     shift; break        ;;
        *)                      break               ;;
    esac done
    _pretty__echo "$@"
    $doexit && exit "$es"
    return "$es"
}


think() {
    #
    # If verbose is on, think loud
    #
    # Use "-l" to split every parameter to separate line, (useful
    # or longer warnings)
    #
    test "$PRETTY_VERBOSE" == true || return 0
    _pretty__echo "$@"
}


warn() {
    #
    # Warn them
    #
    # Use "-l" to split every parameter to separate line, (useful
    # or longer warnings)
    #
    _pretty__echo "$@"
}


##----------##
## BACK-END ##
##----------##


_pretty__cat() {
    #
    # `cat` but without starting a process
    #
    # Used to avoid spanning new process where stream handler is chosen
    # based on some logic
    #
    while IFS= read -r line;
    do echos "$line"; done
}


_pretty__get_caller() {
    #
    # Get first user function and negative index from stack
    #
    local fname
    local nidx="${#FUNCNAME[@]}"
    for fname in "${FUNCNAME[@]}"; do
        (( nidx-- ))
        _pretty__is_internal && continue
        _pretty__is_frontend && continue
        test "$fname" = "usage" && continue
        echos "$nidx $fname"
        return
    done
}

_pretty__get_frontend() {
    #
    # Get entry point function name from stack
    #
    local fname
    for fname in "${FUNCNAME[@]}"; do
        _pretty__is_internal && continue
        _pretty__is_frontend && echos "$fname" && return 0
        echo "do not call _pretty_* directly: $fname" >&2
        return "$EXIT_USAGE"
    done
}

_pretty__is_excluded() {
    #
    # True if $caller is excluded based on PRETTY_DEBUG_EXCLUDE
    #
    # Check PRETTY_DEBUG_EXCLUDE to see if $caller (using only module name
    # part, if possible) should be muted from debugging.
    #
    local listed        # item listed in PRETTY_DEBUG_EXCLUDE
    local name          # module part of caller's name
    local qualified     # is caller "qualified" (ac. to shellfu scheme)?
    name="$caller"
    case "$name" in
        __*__*) qualified=true  ;;
        __*)    qualified=false ;;
        *__*)   qualified=true  ;;
        *)      qualified=false ;;
    esac
    if $qualified; then
        # we'll use only the module part of the name
        name=${name#_}      # drop one "internal" prefix
        name=${name#_}      # drop yet another one
        name=${name%%__*}   # drop funcname
    fi
    for listed in ${PRETTY_DEBUG_EXCLUDE//,/ }; do
        test "$name" = "$listed" && return 0
    done
    return 1
}

_pretty__is_frontend() {
    #
    # True if $fname is one of our "frontends"
    #
    case "$fname" in
        debug)      return 0 ;;
        debug_pipe) return 0 ;;
        die)        return 0 ;;
        mkhelp)     return 0 ;;
        think)      return 0 ;;
        mkusage)    return 0 ;;
        warn)       return 0 ;;
    esac
    return 1
}

_pretty__is_internal() {
    #
    # True if $fname is our internal function
    #
    case "$fname" in
        _pretty__*) return 0 ;;
        *)          return 1 ;;
    esac
}

_pretty__echo() {
    #
    # A smarter echo backend
    #
    # A smarter backend for debug, warn, think, die and
    # mkusage.
    #
    #   -c cmd      echo output of a command
    #   -f file     echo output of a file (- for stdin)
    #   -l line [line...] echo each line separately
    #   -t          add stack trace to output
    #   -u patt [patt...] convert each patt to usage pattern
    #   -v var [var...] show contents of each var
    #
    local frontend  # who (of pretty.sh) was called (=> prettyprinter choice)
    local caller    # which user's function (or script) called it
    #     ^      ^    eg. if user calls 'debug hello' from function 'foo', then
    #     :      :..   *  frontend is 'debug'
    #     :.........   *  and caller is 'foo'.
    local caller_nidx       # negative stack index of caller
    local caller_is_main    # true if caller was main script or main() in it
    local provider          # which provider (_pretty__echo_*()) to use
    frontend="$(_pretty__get_frontend)" || exit_usage
    read -r caller_nidx caller <<<"$(_pretty__get_caller)"
    test "$frontend" = debug && _pretty__is_excluded "$caller" && return 0
    #shellcheck disable=SC2034
    case $caller_nidx:$caller in
        0:*)        caller_is_main=true; caller="${0##*/}" ;;
        1:main)     caller_is_main=true; caller="${0##*/}" ;;
        *:usage)    frontend=mkusage                       ;;
        *)          caller_is_main=false                   ;;
    esac
    while true; do case $1 in
        -c|--cmd)   provider=cmd;   shift; break ;;
        -f|--files) provider=files; shift; break ;;
        -l|--lines) provider=lines; shift; break ;;
        -t|--trace) provider=trace; shift; break ;;
        -u|--usage) provider=usage; shift; break ;;
        -v|--vars)  provider=vars;  shift; break ;;
        *)          provider=args;         break ;;
    esac done
    _pretty__echo_$provider "$@" \
      | _pretty__$frontend >&2
}


_pretty__echo_args() {
    #
    # The simplest (but safe) printing of args
    #
    echos "$*"
}


_pretty__echo_cmd() {
    #
    # Print command line, launch it and report exit status
    #
    local es
    echo "-- begin command $* --"
    "$@"; es=$?
    echo "-- end command ($es) $* --"
}


_pretty__echo_files() {
    #
    # Print names and contents of existing files
    #
    local fp
    for fp in "$@"; do
        if test "$fp" = "-"; then
            echo "-- begin pipe --"
            cat
            echo "-- end pipe --"
        elif test -s "$fp" || test "$fp" = "/dev/stdin"; then
            echo "-- begin file $fp --"
            cat "$fp"
            echo "-- end file $fp --"
        fi
    done
}


_pretty__echo_lines() {
    #
    # Echo each argument as a separate line
    #
    local l;
    for l in "$@"; do _pretty__echo_args "$l"; done
}


_pretty__echo_trace() {
    #
    # Print "decorated" call trace (only in debug mode)
    #
    test "$PRETTY_DEBUG" == true || return 0
    local depth
    echo "== trace =="
    for depth in $(seq 0 ${#FUNCNAME}); do
        caller "$depth" || break
    done \
      | tail -n +3 \
      | sed -e '
            s/^\([^ ]\+\) \([^ ]\+\) \(.*\)/\3:\1:\2()/
            #  ^line^,    ^func^,    ^file^
            1   s/^/ -> /g
            2,$ s/^/    /
        ' \
      | tac
}


_pretty__echo_help() {
    local oldverbose="$PRETTY_VERBOSE"
    think -l "$@"
    PRETTY_VERBOSE=$oldverbose
}

_pretty__echo_usage() {
    #
    # Compose conventional usage guide
    #
    # The default mode treats each argument as usage pattern
    # (see below for details).  Additional formatting can be
    # conveniently achieved by switching to other modes, which
    # automatically brings necessary headers and indentations
    # where needed.
    #
    #  *  option mode (`-o`) prints "options:" header and 
    #     indents next arguments,
    #
    #  *  command mode (`-c`) prints "commands:" header and
    #     indents next arguments,
    #
    #  *  indent mode (`-i`) just indents next arguments,
    #
    #  *  plain mode (`--`) prints empty line (new paragraph)
    #     and turns indentations off.
    #
    #  *  usage mode (`-u`, active by default), prints
    #     "usage:" header, indents next arguments and prefixes
    #     them with name of the script.  See also $PRETTY_USAGE.
    #
    #     A special case of usage mode is when only single
    #     argument is passed to this function; then instead
    #     printing "usage:" header on separate string, it is
    #     joined with the argument to single line.
    #
    # In order to help avoid (rare) conflict between mkusage()
    # switches and your usage patterns, the very first argument,
    # and each argument that comes right after one of these
    # switches are guarranteed not to be interpreted as switch.
    #
    local self          # the script name
    local mode=usage    # mode
    local esc=1         # escape (take next argument as literal)
    local arg           # argument to iterate
    case "$PRETTY_USAGE" in
        self=*)     self=${PRETTY_USAGE#self=}          ;;
        subcommand) self="${0##*/}"; self="${self/-/ }" ;;
        *)          self="$caller" ;;
    esac
    case $# in
        0)  return 0 ;;
        1)  echo "usage: $self $1"; return 0 ;;
    esac
    echo usage:
    for arg in "$@"; do
        case $esc:$arg in
            0:--) shift; mode=plain;  esc=1; echo                ;;
            0:-c) shift; mode=indent; esc=1; echo; echo commands: ;;
            0:-i) shift; mode=indent; esc=1                      ;;
            0:-o) shift; mode=indent; esc=1; echo; echo options: ;;
            0:-u) shift; mode=usage;  esc=1                      ;;
            *)  esc=0
                case $mode in
                    usage)  echo  "  $self $arg" ;;
                    indent) echo  "  $arg" ;;
                    plain)  echos "$arg" ;;
                esac
                ;;
        esac
    done
}


_pretty__echo_vars() {
    #
    # Report value of each named variable
    #
    local varname
    local declare_str
    for varname in "$@"; do
        if ! _pretty__is_word "$varname"; then
            warn "unsafe value skipped: $varname";
            continue
        fi
        if declare_str=$(declare -p "$varname" 2>/dev/null); then
            _pretty__echo "${declare_str#declare ?? }"
        else
            _pretty__echo "$varname #Unset"
        fi
    done
}


_pretty__is_word() {
    #
    # Check if $1 contains only alphanumeric chars or _
    #
    local tainted="$1"
    local clean
    clean=$(tr -c -d '_[:alnum:]' <<< "$tainted")
    test "$tainted" = "$clean"
}