1"""
2Utilities for truncating assertion output.
3
4Current default behaviour is to truncate assertion explanations at
5~8 terminal lines, unless running in "-vv" mode or running on CI.
6"""
7from __future__ import absolute_import, division, print_function
8import os
9
10import six
11
12
13DEFAULT_MAX_LINES = 8
14DEFAULT_MAX_CHARS = 8 * 80
15USAGE_MSG = "use '-vv' to show"
16
17
18def truncate_if_required(explanation, item, max_length=None):
19    """
20    Truncate this assertion explanation if the given test item is eligible.
21    """
22    if _should_truncate_item(item):
23        return _truncate_explanation(explanation)
24    return explanation
25
26
27def _should_truncate_item(item):
28    """
29    Whether or not this test item is eligible for truncation.
30    """
31    verbose = item.config.option.verbose
32    return verbose < 2 and not _running_on_ci()
33
34
35def _running_on_ci():
36    """Check if we're currently running on a CI system."""
37    env_vars = ['CI', 'BUILD_NUMBER']
38    return any(var in os.environ for var in env_vars)
39
40
41def _truncate_explanation(input_lines, max_lines=None, max_chars=None):
42    """
43    Truncate given list of strings that makes up the assertion explanation.
44
45    Truncates to either 8 lines, or 640 characters - whichever the input reaches
46    first. The remaining lines will be replaced by a usage message.
47    """
48
49    if max_lines is None:
50        max_lines = DEFAULT_MAX_LINES
51    if max_chars is None:
52        max_chars = DEFAULT_MAX_CHARS
53
54    # Check if truncation required
55    input_char_count = len("".join(input_lines))
56    if len(input_lines) <= max_lines and input_char_count <= max_chars:
57        return input_lines
58
59    # Truncate first to max_lines, and then truncate to max_chars if max_chars
60    # is exceeded.
61    truncated_explanation = input_lines[:max_lines]
62    truncated_explanation = _truncate_by_char_count(truncated_explanation, max_chars)
63
64    # Add ellipsis to final line
65    truncated_explanation[-1] = truncated_explanation[-1] + "..."
66
67    # Append useful message to explanation
68    truncated_line_count = len(input_lines) - len(truncated_explanation)
69    truncated_line_count += 1  # Account for the part-truncated final line
70    msg = '...Full output truncated'
71    if truncated_line_count == 1:
72        msg += ' ({0} line hidden)'.format(truncated_line_count)
73    else:
74        msg += ' ({0} lines hidden)'.format(truncated_line_count)
75    msg += ", {0}" .format(USAGE_MSG)
76    truncated_explanation.extend([
77        six.text_type(""),
78        six.text_type(msg),
79    ])
80    return truncated_explanation
81
82
83def _truncate_by_char_count(input_lines, max_chars):
84    # Check if truncation required
85    if len("".join(input_lines)) <= max_chars:
86        return input_lines
87
88    # Find point at which input length exceeds total allowed length
89    iterated_char_count = 0
90    for iterated_index, input_line in enumerate(input_lines):
91        if iterated_char_count + len(input_line) > max_chars:
92            break
93        iterated_char_count += len(input_line)
94
95    # Create truncated explanation with modified final line
96    truncated_result = input_lines[:iterated_index]
97    final_line = input_lines[iterated_index]
98    if final_line:
99        final_line_truncate_point = max_chars - iterated_char_count
100        final_line = final_line[:final_line_truncate_point]
101    truncated_result.append(final_line)
102    return truncated_result
103