# Copyright 2022 Google LLC. This software is provided as is, without warranty
# or representation for any use or purpose.
# Your use of it is subject to your agreement with Google.

import csv
import re
import os

def clean_input(arg):
    return arg.strip().replace('\n', '')


def parse_import_statement(import_statement):
    pattern = r'^(?:from\s+([\w.]+)\s+)?import\s+(?:\(([^)]+)\)|([\w., ]+))$'
    match = re.search(pattern, import_statement)

    if match:
        mod_name = match.group(1)
        imported_names = match.group(2) or match.group(3)
        if imported_names:
            imported_names = re.findall(r'([\w.]+)(?:\s+as\s+[\w.]+)?', imported_names)
        return mod_name, imported_names
    else:
        return None, None


class MigrationUtility:
    def __init__(self, input_dir, output_dir, rules_file, add_comments, comments, report_generation):
        self.replacement_dict = {}
        self.rules_file = rules_file
        self.input_dir = input_dir
        self.output_dir = output_dir
        self.add_comments = add_comments
        self.comments = comments
        self.report_generation = report_generation
        self.function_regex = r'(\w+(?:\.\w+)*)\('

    def load_rules(self):
        with open(self.rules_file, 'r') as f:
            reader = csv.reader(f)
            for col in reader:
                self.replacement_dict[col[2].strip()] = (clean_input(col[0]), clean_input(col[1]), clean_input(col[3]),
                                                         clean_input(col[4]), clean_input(col[5]), clean_input(col[6]))

    @staticmethod
    def print_report(impacted_files):
        # temp method to print report on console , will modify this in phase 2
        print("#" * 40)
        print("          REPORT GENERATION           ")
        print("#" * 40)
        print()

        print('Below is the list of impacted files')
        print(f'Total number of impacted files is - {len(impacted_files)}')
        file_string = '\n '.join(impacted_files)
        print(file_string)
        # Conclusion
        print("#" * 40)
        print("             END OF REPORT             ")
        print("#" * 40)

    def migrate_files(self, comment_flag, comment):
        impacted_files = []
        change_count = 0
        inp_len = len(self.input_dir)
        for root,dirs,files in os.walk(self.input_dir):
            for file in files:
                if file.endswith(".py"):
                    filepath =  root + "/"+file
                    new_dir = self.output_dir+root[inp_len:]
                    isExist = os.path.exists(new_dir)
                    if not isExist:
                        os.makedirs(new_dir)
                    new_file = new_dir+"/"+file
                    change_count = 0
                    with open(filepath, 'r') as f, open(new_file, 'w') as temp:
                        for line in f:
                            # check if a comment
                            # add feature to identify multi-line comments and ignore
                            if line.startswith('#'):
                                temp.write(line)
                                continue
                            # check if this is an import statement
                            mod_name, imported_names = parse_import_statement(line)
                            if mod_name is not None:
                                tmpLine = ''
                                for idx, rec in enumerate(imported_names):
                                    imp_stmt = ''
                                    if mod_name:
                                        imp_stmt = 'from ' + mod_name + ' '
                                    imp_stmt += 'import ' + rec
                                    if imp_stmt in self.replacement_dict:
                                        change_count += 1
                                        if self.add_comments:
                                            if self.comments:
                                                comment = '# ' + self.comments + '\n'
                                            else:
                                                comment = '# Migration Utility Generated Comment -- Change Type = ' + \
                                                    self.replacement_dict[imp_stmt][1] + " , Impact = " + \
                                                    self.replacement_dict[imp_stmt][3] + '\n'
                                            temp.write(comment)
                                        tmpLine = tmpLine + self.replacement_dict[imp_stmt][2] + '\n'
                                    else:
                                        tmpLine = line
                                line = tmpLine
                            else:
                                # extract function call
                                matches = re.findall(self.function_regex, line)

                                if matches:
                                    # search if required to replace
                                    for rec in matches:
                                        if rec in self.replacement_dict:
                                            change_count += 1
                                            if self.add_comments:
                                                if self.comments:
                                                    comment = '# ' + self.comments + '\n'
                                                else:
                                                    comment = '# Migration Utility Generated Comment -- Change Type = ' + \
                                                            self.replacement_dict[rec][1] + " , Impact = " + \
                                                            self.replacement_dict[rec][3] + '\n'
                                                temp.write(comment)
                                            line = line.replace(rec, self.replacement_dict[rec][2])
                                        if rec+"(" in self.replacement_dict or rec+" (" in self.replacement_dict:
                                            change_count +=1
                                            space_count = len(line) - len(line.lstrip())
                                            spaces=''
                                            for i in range(space_count+4) :
                                                spaces = ' '+spaces
                                            if self.add_comments:
                                                if self.comments:
                                                    comment = '# ' + self.comments + '\n'
                                                else:
                                                    comment = '# Migration Utility Generated Comment -- Change Type = ' + \
                                                        self.replacement_dict[rec+"("][1] + " , Impact = " + \
                                                        self.replacement_dict[rec+"("][3] + '\n'
                                                temp.write(comment)
                                            line = line+spaces +self.replacement_dict[rec+"("][2]+",\n"
                            
                            for word, replacement in self.replacement_dict.items():
                                if replacement[1] == "Argument Replace" and replacement[4] == "TRUE" and replacement[5] == "FALSE":
                                    if word in line:
                                        change_count +=1
                                        if self.add_comments:
                                            if self.comments:
                                                comment = '# ' + self.comments + '\n'
                                            else:
                                                comment = '# Migration Utility Generated Comment -- Change Type = ' + \
                                                        replacement[1] + " , Impact = " + \
                                                        replacement[3] + '\n'
                                            temp.write(comment)
                                        line = line.replace(word,replacement[2])
                                        break

                            temp.write(line)

                    if change_count > 0:
                        impacted_files.append(file)
        if self.report_generation:
            self.print_report(impacted_files)


def run_migration(input_dag, output_dag, rules_file, add_comments, comments, report_generation):
    migration_utility = MigrationUtility(input_dir=input_dag, output_dir=output_dag,
                                         rules_file=rules_file, add_comments=add_comments,
                                         comments=comments, report_generation= report_generation)
    migration_utility.load_rules()
    migration_utility.migrate_files(add_comments, comments)