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