templating_engine.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import re, sys, json

default_stream = \
"""
"header": "Hello!"
"somearray": ["apple", "banana", "citrus", "dog"]
"footer": "That's it!"
"condition": "True"
"result": "You win!"
"""

default_template = \
"""
First line.
{{header}}
{{#loop somearray item}}
This is a {{item}}.
{{#if condition result}}
This is {{result}}.
{{footer}}
Last line.
"""

def interpret(t, i):
    """
    This function filters the layout according to the default template and outputs
    it to stdout. It will strings, ints, and floats to the command line as printed text.
    It loops through an array and prints out each elements using the specified notation.
    {{#loop somearray item}}  
    Please note that this does 
    IT also takes a boolean condition and prints a result, both passed in from the stream.
    """

    ## Variables
    template_add = {}
    next_row_skip = [-1]

    ## v: stream by row. if by file, then use enumerate(v.splitlines(True))
    template = list(filter(None, list(t.split('\n'))))
    for k,y in enumerate(i):

        if 'header' in y.keys() \
        or 'footer' in y.keys():
            replace_with = str(list(y.values())[0])
            replace_this = str(list(y.keys())[0])
            template_add[replace_this] = replace_with
        if 'condition' in y.keys():
            replace_with = str(y.values())
            replace_this = str(y.keys())
            template_add[replace_this] = replace_with
        if 'result' in y.keys():
            replace_this = str(list(y.keys())[0])
            replace_with = list(y.values())[0]
            template_add[replace_this] = replace_with
        elif isinstance(list(y.values())[0], list) == True:
            replace_this = str(list(y.keys())[0])
            replace_with = list(y.values())[0]
            template_add[replace_this] = replace_with

        elif isinstance(list(y.values())[0], int) == True:
            replace_with = list(y.values())[0]
            replace_this = str(list(y.keys())[0])
            template_add[replace_this] = replace_with

        else:
            ## default type set: string
            replace_with = str(list(y.values())[0])
            replace_this = str(list(y.keys())[0])
            template_add[replace_this] = replace_with
        #print(":::::::::::::::::::::template")
        #print(template)
    # <!-- end: build template_add -->

    for this_row_id, this_row_data in enumerate(template):
      try:
        ## future: recursive functions for sections with nested loops
        i=1
        now_this_row_id = this_row_id

        if this_row_data == '{{header}}' \
        or this_row_data == '{{footer}}':
            this_row_data = this_row_data.replace(
                                '{{header}}', template_add['header']).replace(
                                '{{footer}}', template_add['footer'])
        if this_row_data == '{{condition}}' \
        or this_row_data == '{{result}}':
           this_row_data = this_row_data.replace(
                              '{{condition}}', template_add['condition']).replace(
                              '{{result}}', template_add['result'])

        #print("::::::::::::::::templating debug")
        #print(this_row_id, this_row_data)
        ## {{#loop somearray item}}
        ## Note this does not handle nested functions.
        rx = re.findall(r"^{{#loop (\w+) (\w+)", this_row_data)
        if rx:
            rx_key = rx[0][0]               # somearray
            rx_val = template_add[rx_key]   # list()
            tx_rex = rx[0][1]               # item
            tx_mex = "{{" + tx_rex + "}}"   # {{item}}
            this_row_data = ""
            replace_next_row = template[now_this_row_id+1]
            next_row_skip.append(now_this_row_id+i)

            for abc,xyz in enumerate(rx_val):
                this_row_data += replace_next_row.replace(tx_mex, str(xyz))+"\n"
        #{{#if condition result}}
        rx = re.findall("^{{#if (\w+) (\w+)", this_row_data)
        if rx:
            rx_key = rx[0][0]               # condition
            rx_val = template_add[str(rx_key)]   # bool
            tx_rex = rx[0][1]               # result
            tx_mex = "{{" + tx_rex + "}}"   # {{result}}
            this_row_data = ""
            replace_next_row = template[now_this_row_id+1]
            next_row_skip.append(now_this_row_id+i)        
            
            if eval(rx_val):
                this_row_data += replace_next_row.replace(tx_mex, rx_val)+"\n"

        ## <!-- end: use template_add -->

      except (IndexError) as e:
        pass

      ## skip rows, strip dupe newlines, append to final output_result
      try:
        if this_row_id in next_row_skip:
          # Row: Nothing appended to final output
          next_row_skip.remove(this_row_id)
        else:
          # Row: Appending data to final output
          if not this_row_data == "":
            pass
          output_result += this_row_data.rstrip("\n") + "\n"
      except (NameError) as e:
        if (next_row_skip == this_row_id):
          # Row: Nothing appended to final output
          continue
        else:
          # Row: Created row 1
          output_result = this_row_data + "\n"
          # Idx: Removed placeholder -1
          next_row_skip.remove(-1)

    return output_result
## <!-- end: filter_layout_template -->

def split_input_stream(x):
    return filter(None, list(x.split('\n')))

def json_input_stream(x):
    return [ json.loads("{" + str(i) + "}") for i in x ]

def read_input_stream():
    input_stream = sys.stdin.read()
    return input_stream

if __name__ == '__main__':

    #input_stream = default_stream
    input_stream = read_input_stream()
    layout_template = default_template
    input_stream_list = split_input_stream(input_stream)

    input_stream_json = json_input_stream(input_stream_list)

    layout_template_list = interpret(layout_template,
                                                  input_stream_json)
    print(layout_template_list)