#!/bin/bash


usage() {
    local self
    self="$(basename "$0")"
    warn "usage: $self [-f|--force] [+TEMPLATE] FILE"
    warn "usage: $self -l|--list"
    exit 2
}

warn() {
    #
    # Print warning
    #
    echo "$@" >&2
}

die() {
    #
    # Warn and exit prematurely
    #
    warn "$@"
    exit 3
}

lstemplates() {
    #
    # Print list of valid templates
    #
    echo sed
    echo pya
    echo shellfu
    echo Bash
    echo Lua
    echo Perl
    echo py3
    echo Python3
    echo Python
}

#shellcheck disable=SC2016
mktemplate() {
    #
    # Print template $Template for $FilePath
    #
    case "$Template" in

        sh)
            echo "#!/bin/sh"
            echo ''
            echo ''
            ;;

        bash|Bash)
            echo "#!/bin/bash"
            echo ''
            echo ''
            ;;

        sed)
            echo "#!/bin/sed -f"
            echo ''
            echo ''
            ;;

        lua|Lua)
            echo "#!$(which lua)"
            echo ''
            ;;

        pl|Perl)
            echo "#!$(which perl)"
            echo ''
            echo 'use strict;'
            echo 'use warnings;'
            echo ''
            echo ''
            ;;

        py|Python)
            echo "#!$(which python)"
            echo ''
            echo "if __name__ == '__main__':"
            echo '    '
            ;;

        py3|Python3)
            echo "#!/usr/bin/python3"
            echo ''
            echo 'import sys'
            echo ''
            echo ''
            echo 'class UsageError(ValueError):'
            echo '    pass'
            echo ''
            echo ''
            echo 'def usage():'
            echo '    self = sys.argv[0]'
            echo '    raise UsageError("usage: %s [-j|-t|-p] YAML_FILE.." % self)'
            echo ''
            echo ''
            echo 'def main(argv):'
            echo '    if len(argv) < 2:'
            echo '        usage()'
            echo ''
            echo ''
            echo 'if __name__ == "__main__":'
            echo '    main(sys.argv[1:])'
            ;;

        pya)
            echo '#!/usr/bin/python3'
            echo '"""'
            echo 'A simple application'
            echo '"""'
            echo ''
            echo 'import sys'
            echo 'import traceback'
            echo ''
            echo ''
            echo 'class UsageError(ValueError):'
            echo '    pass'
            echo ''
            echo ''
            echo 'class AppError(RuntimeError):'
            echo '    pass'
            echo ''
            echo ''
            echo 'class BaseApp:'
            echo '    """'
            echo '    Main application class'
            echo '    """'
            echo ''
            echo '    @classmethod'
            echo '    def main(cls, factory=None):'
            echo '        factory = factory if factory else cls.from_argv'
            echo '        try:'
            echo '            app = factory()'
            echo '            es = app.run()'
            echo '        except UsageError as e:'
            echo '            print(e, file=sys.stderr)'
            echo '            sys.exit(2)'
            echo '        except AppError as e:'
            echo '            print(e, file=sys.stderr)'
            echo '            sys.exit(3)'
            echo '        except Exception:'
            echo '            sys.stderr.write(traceback.format_exc())'
            echo '            sys.exit(4)'
            echo '        if type(es) is not int:'
            echo '            msg = ('
            echo '                "%s.run() did not return proper exit status: %r is not int"'
            echo '                % (app.__class__.__name__, es)'
            echo '            )'
            echo '            BaseApp.WARN(msg)'
            echo '            es = 4'
            echo '        sys.exit(es)'
            echo ''
            echo '    @classmethod'
            echo '    def from_argv(cls):'
            echo '        return cls('
            echo '            name=sys.argv[0],'
            echo '            args=sys.argv[1:]'
            echo '        )'
            echo ''
            echo '    def __init__(self, name, args):'
            echo '        self.name = name'
            echo '        self.args = args'
            echo ''
            echo '    def _throw_usage(self, pattern=None):'
            echo '        """'
            echo '        Throw UsageError with pattern *pattern*.'
            echo '        """'
            echo '        parts = ["usage:", self.name]'
            echo '        if pattern:'
            echo '            parts.append(pattern)'
            echo '        raise UsageError(" ".join(parts))'
            echo ''
            echo '    @staticmethod'
            echo '    def WARN(msg):'
            echo '        """'
            echo '        Warn user with message *msg*.  *msg* can be string or a list of lines.'
            echo '        """'
            echo '        if type(msg) is list:'
            echo '            lines = msg'
            echo '        else:'
            echo '            lines = [str(msg)]'
            echo '        for line in lines:'
            echo '            print(line, file=sys.stderr)'
            echo ''
            echo '    def _validate(self):'
            echo '        """'
            echo '        Validate *self.args*; throw UsageError if needed.'
            echo '        """'
            echo '        if not self.args:'
            echo '            self._throw_usage("ARG..")'
            echo ''
            echo '    def run(self):'
            echo '        """'
            echo '        Run the application; return integer exit status'
            echo '        """'
            echo '        self._validate()'
            echo '        if self.args[0] == "--fail":'
            echo '            raise AppError("you asked for it")'
            echo '        if self.args[0] == "--fail-unexpectedly":'
            echo '            raise RuntimeError("you asked for it ANyway")'
            echo '        if self.args[0] == "--warn":'
            echo '            BaseApp.WARN("you asked for a warning")'
            echo '            return 0'
            echo '        if self.args[0] == "--badret":'
            echo '            return object()'
            echo '        return 0'
            echo ''
            echo ''
            echo 'class App(BaseApp):'
            echo ''
            echo '    def _validate(self):'
            echo '        """'
            echo '        Validate *self.args*; throw UsageError as needed.'
            echo ''
            echo '        Prefer using self._throw_usage().'
            echo '        """'
            echo '        App.WARN("You need to rewrite App._validate()!!!")'
            echo '        super()._validate()'
            echo ''
            echo '    def run(self):'
            echo '        """'
            echo '        Run the application; return integer exit status'
            echo '        """'
            echo '        App.WARN("You need to rewrite App.run()")'
            echo '        super().run()'
            echo ''
            echo ''
            echo 'if __name__ == "__main__":'
            echo '    App.main()'
            ;;

        shellfu)
            echo "#!/bin/bash"
            echo ""
            echo '#shellcheck disable=SC1090'
            echo '. "$(sfpath)" || exit 3'
            echo ''
            echo 'shellfu import pretty'
            echo ''
            echo 'usage() {'
            echo '    mkusage "$@" "[-d] [-v] ARG..."'
            echo '}'
            echo ''
            echo 'main() {'
            echo '    while true; do case $1 in'
            echo '        -d) PRETTY_DEBUG=true;   shift ;;'
            echo '        -v) PRETTY_VERBOSE=true; shift ;;'
            echo '        -*) usage -w "unknown argument: $1" ;;'
            echo '        *)  break ;;'
            echo '    esac done'
            echo '}'
            echo ''
            echo 'main "$@"'
            ;;

        *)
            die "unknown template or language: $Template"
            ;;
    esac
}

guess_language() {
    #
    # Guess intended language from filepath $FilePath
    #
    local fname     # file name
    fname="$(basename "$FilePath")"
    case "$fname" in
        *.*)    echo "${fname##*.}" ;;
        *)      echo "$MKX_DEFAULT_LANG" ;;
    esac
}


#
# Default language
#
MKX_DEFAULT_LANG=${MKX_DEFAULT_LANG:-sh}

main() {
    local FilePath  # destination file path
    local Template  # built-in template name
    local careful     # ignore existing file
    careful=true
    while true; do case $1 in
        -f|--force) careful=false; shift ;;
        -l|--list)  lstemplates; exit 0 ;;
        -*) usage ;;
        +*) Template="${1:1}"; shift ;;
        *)  break ;;
    esac done
    FilePath="$1"
    test -n "$FilePath" || usage
    test -f "$FilePath" && $careful && die "file already exists: $FilePath"
    test -n "$Template" || Template=$(guess_language)
    mktemplate > "$FilePath"
    chmod +x "$FilePath"
}

main "$@"