tied line histogram into txt paragraph structure detection

src/calibre/ebooks/conversion/preprocess.py

@@ -78,6 +78,8 @@ class DocAnalysis(object):
             linere = re.compile('(?<=<br>)(?!\s*<br>).*?(?=<br>)', re.DOTALL)
         elif format == 'spanned_html':
             linere = re.compile('(?<=<span).*?(?=</span>)', re.DOTALL)
+        elif format == 'txt':
+            linere = re.compile('.*?\n', re.DOTALL)
         self.lines = linere.findall(raw)
 
     def line_length(self, percent):

src/calibre/ebooks/txt/input.py

@@ -90,7 +90,7 @@ class TXTInput(InputFormatPlugin):
             
             # We don't check for block because the processor assumes block.
             # single and print at transformed to block for processing.
-            if options.paragraph_type == 'single':
+            if options.paragraph_type == 'single' or 'unformatted':
                 txt = separate_paragraphs_single_line(txt)
             elif options.paragraph_type == 'print':
                 txt = separate_paragraphs_print_formatted(txt)

src/calibre/ebooks/txt/processor.py

@@ -9,6 +9,7 @@ import os, re
 from calibre import prepare_string_for_xml, isbytestring
 from calibre.ebooks.markdown import markdown
 from calibre.ebooks.metadata.opf2 import OPFCreator
+from calibre.ebooks.conversion.preprocess import DocAnalysis
 
 __license__   = 'GPL v3'
 __copyright__ = '2009, John Schember <john@nachtimwald.com>'
@@ -102,13 +103,19 @@ def detect_paragraph_type(txt):
     print: Each paragraph starts with a 2+ spaces or a tab
            and ends when a new paragraph is reached.
     markdown: Markdown formatting is in the document.
+    unformatted: most lines have hard line breaks, few/no spaces or indents
     
-    returns block, single, print, markdown
+    returns block, single, print, markdown, unformatted
     '''
     txt = txt.replace('\r\n', '\n')
     txt = txt.replace('\r', '\n')
     txt_line_count = len(re.findall('(?mu)^\s*.+$', txt))
     
+    # Check for hard line breaks - true if 55% of the doc breaks in the same region
+    docanalysis = DocAnalysis('txt', txt)
+    hardbreaks = docanalysis.line_histogram(.55)
+    
+    if hardbreaks:
         # Check for print
         tab_line_count = len(re.findall('(?mu)^(\t|\s{2,}).+$', txt))
         if tab_line_count / float(txt_line_count) >= .25:
@@ -119,9 +126,13 @@ def detect_paragraph_type(txt):
         if empty_line_count / float(txt_line_count) >= .25:
             return 'block'
 
-    # Nothing else matched to assume single.
+        # Assume unformatted text with hardbreaks if nothing else matches        
+        return 'unformatted'
+    
+    # return single if hardbreaks is false
     return 'single'
 
+
 def detect_formatting_type(txt):
     # Check for markdown
     # Headings