Issue #14: support Memrise data parsing.

Parse user data in the HTML format that contains time and number of tests for
each learning session.

emmio/external/memrise.py

@@ -0,0 +1,84 @@
+from datetime import datetime, timedelta
+from html.parser import HTMLParser
+from typing import Optional
+
+from emmio.ui import log
+
+
+class TableParser(HTMLParser):
+    def __init__(self):
+        super().__init__()
+        self.tables = []
+        self.current_table = []
+        self.current_row = []
+        self.in_td = False
+
+    def error(self, message: str) -> None:
+        log.error(message)
+
+    def handle_starttag(self, tag, attrs) -> None:
+        if tag == "td":
+            self.in_td = True
+
+    def handle_endtag(self, tag) -> None:
+        if tag == "td":
+            self.in_td = False
+        elif tag == "table":
+            if self.current_table:
+                self.tables.append(self.current_table)
+                self.current_table = []
+        elif tag == "tr":
+            if self.current_row:
+                self.current_table.append(self.current_row)
+                self.current_row = []
+
+    def handle_data(self, data) -> None:
+        if self.in_td:
+            self.current_row.append(data.strip())
+
+
+def parse_date(date_string: str) -> Optional[datetime]:
+    for date_format in ["%Y-%m-%d %H:%M:%S.%f", "%Y-%m-%d %H:%M:%S"]:
+        try:
+            return datetime.strptime(date_string, date_format)
+        except ValueError:
+            pass
+
+    return None
+
+
+class MemriseDataRecord:
+    def __init__(
+            self, course_name: str, date_from: datetime, date_to: datetime,
+            num_tests: int, score: float):
+
+        self.course_name = course_name
+        self.date_from = date_from
+        self.date_to = date_to
+        self.num_tests = num_tests
+        self.score = score
+
+
+class MemriseData:
+    def __init__(self, file_name: str):
+        with open(file_name, "r") as input_file:
+            content = input_file.read()
+
+        parser = TableParser()
+        parser.feed(content)
+
+        self.all_tests = 0
+        self.data = []
+
+        for row in parser.tables[4]:
+            course_name, _, from_date, to_date, num_tests, score = row
+
+            if num_tests:
+                self.all_tests += int(num_tests)
+
+            if to_date:
+                f = parse_date(from_date)
+                t = parse_date(to_date)
+
+                self.data.append(MemriseDataRecord(
+                    course_name, f, t, int(num_tests), float(score)))