"""Join dictated single-letter runs before the text model, never after it."""
import re

NORMALIZATION_VERSION = "spelled-letter-runs-v2"

# Horizontal whitespace only: distinct lines/paragraphs are not one spelling run.
_RUN = re.compile(r'(?<![A-Za-z0-9_./:@+\-])(?>[A-Za-z](?:(?:[-‐‑‒–—]|[ \t\u00a0]+)[A-Za-z])+)(?![A-Za-z0-9_./:@+\-])')
_LITERAL = re.compile(
    r'```[\s\S]*?(?:```|\Z)|`[^`\n]*(?:`|\Z)'
    r'|https?://[^\s，。！？；、）]+'
    r'|[A-Za-z0-9._%+\-]+@[A-Za-z0-9.\-]+\.[A-Za-z]{2,}'
    r'|(?:~/|/)[A-Za-z0-9_./~\-]+'
    r'|\b[A-Za-z_]\w*\s*(?:==|!=|<=|>=|:=|[+*/\-]?=)\s*[^;\n，。]+'
)


def spelled_letter_runs(text):
    """Yield unambiguous-enough spelling spans, preserving letter order.

    Three or more separate letters, or two uppercase space-separated letters.
    A two-letter hyphenated expression such as X-Y is left alone.
    Literal code, paths, URLs and emails are not interpreted as dictation.
    """
    literals=[m.span() for m in _LITERAL.finditer(text)]
    for match in _RUN.finditer(text):
        a,b=match.span()
        if any(a<end and b>start for start,end in literals):continue
        letters=re.findall('[A-Za-z]',match[0])
        if len(letters)<3 and not (all(c.isupper() for c in letters) and re.search('[ \t\u00a0]',match[0])):continue
        yield a,b,''.join(letters).lower()


def sentence_start(text,position):
    prefix=text[:position]
    line=prefix.rsplit('\n',1)[-1]
    if re.fullmatch(r"[ \t]*(?:(?:[-*•]|\d+[.)、])[ \t]+)?[“‘\"'「（(\[]*[ \t]*",line):return True
    prefix=prefix.rstrip()
    while prefix and prefix[-1] in '“‘"\'「（([':
        prefix=prefix[:-1].rstrip()
    return not prefix or prefix[-1] in '.!?。！？'


def normalize_spelled_letters(text):
    pieces=[];position=0;count=0
    for start,end,word in spelled_letter_runs(text):
        if sentence_start(text,start):word=word.capitalize()
        pieces.extend([text[position:start],word]);position=end;count+=1
    pieces.append(text[position:])
    return ''.join(pieces),count