#!/bin/bash
# Desc: Utility for backing up and retrieving ots files
# Version: 0.0.1

OTS_FCACHE_DIR="$HOME/.cache/bkotslu/";
MAX_FIND_DEPTH=12;

yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
vbm() {
    # Description: Prints verbose message ("vbm") to stderr if opVerbose is set to "true".
    # Usage: vbm "DEBUG :verbose message here"
    # Version 0.2.0
    # Input: arg1: string
    #        vars: opVerbose
    # Output: stderr
    # Depends: bash 5.1.16, GNU-coreutils 8.30 (echo, date)

    if [ "$opVerbose" = "true" ]; then
	functionTime="$(date --iso-8601=ns)"; # Save current time in nano seconds.
	echo "[$functionTime]:$0:""$*" 1>&2;  # Display argument text.
    fi

    # End function
    return 0; # Function finished.
}; # Displays message if opVerbose true
showUsage() {
    # Desc: Display script usage information
    # Usage: showUsage
    # Version 0.0.2
    # Input: none
    # Output: stdout
    # Depends: GNU-coreutils 8.30 (cat)
    cat <<'EOF'
    USAGE:
        bkotslu [ options ] [FILE...]

    OPTIONS:
        -h, --help
                Display help information.
        --version
                Display script version.
        -v, --verbose
                Display debugging info.
        -i, --input-file
                Define input file path for file to add ots file to.
        -O, --output-dir
                Define output directory path for storing ots backup files.
                  DEFAULT: $HOME/.cache/bkotslu/
        --
                Indicate end of options.

    EXAMPLE:
      Hash foo.txt and lookup matching ots file
        bkotslu -i foo.txt

      Archive ots files from home directory
        bkotslu -I $HOME/

EOF
}; # Display information on how to use this script.
showVersion() {
    # Desc: Displays script version and license information.
    # Usage: showVersion
    # Version: 0.0.2
    # Input: scriptVersion   var containing version string
    # Output: stdout
    # Depends: vbm(), yell, GNU-coreutils 8.30

    # Initialize function
    vbm "DEBUG:showVersion function called."

    cat <<'EOF'
bkotslu 0.0.1
Copyright (C) 2024 Steven Baltakatei Sandoval
License GPLv3: GNU GPL version 3
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

    GNU Coreutils 8.32
    Copyright (C) 2020 Free Software Foundation, Inc.
    License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
    This is free software: you are free to change and redistribute it.
    There is NO WARRANTY, to the extent permitted by law.
EOF
    
    # End function
    vbm "DEBUG:showVersion function ended."
    return 0; # Function finished.
}; # Display script version.
processArgs() {
    # Desc: Processes arguments provided to script.
    # Usage: processArgs "$@"
    # Version: 1.0.0
    # Input: "$@"          (list of arguments provided to the function)
    # Output: Sets following variables used by other functions:
    #   opVerbose            Indicates verbose mode enable status.  (ex: "true", "false")
    #   pathDirOut1          Path to output directory.
    #   pathDirIn1           Path to input directory.
    #   pathFileIn1          Path to input file.
    #   arrayPosArgs         Array of remaining positional argments
    # Depends:
    #   yell()           Displays messages to stderr.
    #   vbm()            Displays messsages to stderr if opVerbose set to "true".
    #   showUsage()      Displays usage information about parent script.
    #   showVersion()    Displays version about parent script.
    #   arrayPosArgs     Global array for storing non-option positional arguments (i.e. arguments following the `--` option).
    # External dependencies: bash (5.1.16), echo
    # Ref./Attrib.:
    #  [1]: Marco Aurelio (2014-05-08). "echo that outputs to stderr". https://stackoverflow.com/a/23550347
    #  [2]: "Handling positional parameters" (2018-05-12). https://wiki.bash-hackers.org/scripting/posparams

    # Initialize function
    vbm "DEBUG:processArgs function called."

    # Perform work
    if [ $# -le 0 ]; then yell "FATAL:No arguments provided."; showUsage; fi;
    while [ ! $# -eq 0 ]; do   # While number of arguments ($#) is not (!) equal to (-eq) zero (0).
	#yell "DEBUG:Starting processArgs while loop." # Debug stderr message. See [1].
        #yell "DEBUG:Provided arguments are:""$*"      # Debug stderr message. See [1].
	case "$1" in
	    -h | --help) showUsage; exit 1;; # Display usage.
	    --version) showVersion; exit 1;; # Show version
	    -v | --verbose) opVerbose="true"; vbm "DEBUG:Verbose mode enabled.";; # Enable verbose mode. See [1].
	    -i | --input-file) # Define input file path
		if [ -f "$2" ]; then # If $2 is file that exists, set pathFileIn1 to $2, pop $2.
		    pathFileIn1="$2";
                    vbm "DEBUG:Input file pathFileIn1 set to:${pathFileIn1}";
		    shift;
		else
		    die "FATAL: Specified input file does not exist:$2";
		fi;; 
	    -I | --input-dir) # Define input directory path
		if [ -d "$2" ]; then # If $2 is dir that exists, set pathDirIn1 to $2, pop $2.
		    pathDirIn1="$2";
                    vbm "DEBUG:Input directory pathDirIn1 set to:${pathDirIn1}";
		    shift;		    
		else # Display error if $2 is not a valid dir.
		    die "FATAL:Specified input directory does not exist:$2";
		fi;;
	    -O | --output-dir) # Define output directory path
		if [ -d "$2" ]; then # If $2 is dir that exists, set pathDirOut1 to $2, pop $2
		    pathDirOut1="$2";
                    vbm "DEBUG:Output directory pathDirOut1 set to:${pathDirOut1}";
		    shift;		    
		else
		    die "FATAL:Specified output directory is not valid:$2";
		fi;;
            --) # End of all options. See [2].
                shift;
                for arg in "$@"; do
                    vbm "DEBUG:adding to arrayPosArgs:$arg";
                    arrayPosArgs+=("$arg");
                done;
                break;;
            -*) showUsage; die "FATAL: Unrecognized option.";; # Display usage
	    *) showUsage; die "FATAL: Unrecognized argument.";; # Handle unrecognized options. See [1].
	esac;
	shift;
    done;

    ## Identify ots file cache dir
    if [[ -z "$pathDirOut1" ]]; then
        vbm "STATUS:No output directory for caching OTS files specified.";
        pathDirOut1="$OTS_FCACHE_DIR";
        vbm "STATUS:Assuming OTS files to be cached in:${pathDirOut1}";
    fi;
    ## Create cache dir if necessary
    if [[ ! -d "$pathDirOut1" ]]; then
        vbm "STATUS:Creating OTS file cache directory:${pathDirOut1}";
        must mkdir -p "$pathDirOut1";
    fi;
    
    # End function
    vbm "DEBUG:processArgs function ended.";
    return  0; # Function finished.
}; # Evaluate script options from positional arguments (ex: $1, $2, $3, etc.).
get_ots_filehash() {
    # Desc: Gets hash of an opentimestamp'd file from ots file
    # Usage: get_ots_filehash FILE
    # Example: get_ots_filehash foo.txt.ots
    # Depends: ots 0.7.0, GNU grep 3.7, GNU Coreutils 8.32
    #          vbm()              verbose output
    #          BK-2020-03  yell()
    # Input:  arg1    OTS file path
    # Output: stdout  sha256 file hash (lowercase)
    local output;

    vbm "DEBUG:Starting get_ots_filehash() on:$1";
    if output="$( "$(which ots)" info "$1" | \
            grep -E "^File sha256 hash: " | \
            head -n1 | \
            sed -E -e 's/(^File sha256 hash: )([0-9a-f]+$)/\2/g'; )" && \
            [[ -n "$output" ]]; then
        vbm "STATUS:Read file hash via ots from:$1";
        printf "%s" "$output";
        return 0;
    else
        yell "ERROR:Encountered problem getting file hash via ots from:$1";
        return 1;
    fi;
}; # Gets hash of file from ots file
get_ots_oldestblock() {
    # Desc: Gets earliest Bitcoin block number from ots file
    # Usage: get_ots_oldestblock FILE
    # Example: get_ots_oldestblock foo.txt.ots
    # Input: arg1     path  OTS file path
    # Output: stdout  int   Bitcoin block number
    # Depends: OpenTimestamps 0.7.0, GNU grep 3.7, GNU Coreutils 8.32
    #          vbm()
    #          BK-2020-03: yell()
    local output;

    vbm "DEBUG:Starting get_ots_oldestblock() on:$1";    
    if output="$( "$(which ots)" info "$1" | \
            grep -E "verify BitcoinBlockHeaderAttestation\([0-9]+\)" | \
            sort | head -n1 | \
            sed -E -e 's/(^    verify BitcoinBlockHeaderAttestation)\(([0-9]+)(\))/\2/g'; )" && \
            [[ -n "$output" ]]; then
        vbm "STATUS:Retrieved Bitcoin block via ots from:$1";
        printf "%s" "$output";
        return 0;
    else
        yell "ERROR:Encountered problem getting Bitcoin block number via ots from:$1";
        return 1;
    fi;
}; # Gets oldest Bitcoin block from ots file
cache_ots_file() {
    # Desc: Scans and caches an OTS file for storing
    if fhash="$(must get_ots_filehash "$line")" && \
            block="$(must get_ots_oldestblock "$line")"; then
        fout="${fhash}_${block}.otsu"; # file name out
        pout="${pathDirOut1}/${fout}"; # file path out
        vbm "STATUS:Found OTS file at ${line} with hash ${fhash} and block ${block} and saving to ${pout}";
        must cp -n "$line" "$pout";
    else
        yell "ERROR:Problem analyzing file with OpenTimestamps:${line}";
    fi;
}; # Scans a single OTS file

main() {
    processArgs "$@";


    # Scan provided dir for OTS files to cache.
    if [[ -n "$pathDirIn1" ]]; then
        while read -r line; do
            line="$(readlink -f "$line")";
            cache_ots_file;
        done < <(find "$pathDirIn1" -maxdepth "$MAX_FIND_DEPTH" -type f -name "*.ots");
    fi;

    # Lookup OTS file from archive for provided file.
    if [[ -n "$pathFileIn1" ]]; then
        :
    fi;
    
    


}; # main program

main "$@";