"""
Reusable helpers for applying CR changes to TS DOCX files.
Supports both direct editing AND tracked changes (review mode).
"""

import copy
import difflib
import re

from docx.oxml.ns import qn
from docx.oxml import OxmlElement

AUTHOR = "CR Application"
DATE   = "2026-03-24T00:00:00Z"


# ── Revision ID counter ───────────────────────────────────────────────────────

def _get_max_id(doc):
    max_id = 0
    for el in doc.element.body.iter():
        for key, val in el.attrib.items():
            if key.endswith('}id'):
                try:
                    max_id = max(max_id, int(val))
                except ValueError:
                    pass
    return max_id

class RevCounter:
    """Generates unique revision IDs that don't clash with existing ones."""
    def __init__(self, doc):
        self._n = _get_max_id(doc) + 1

    def next(self):
        n = self._n
        self._n += 1
        return str(n)


# ── Helpers ───────────────────────────────────────────────────────────────────

def _make_t(text, tag='w:t'):
    t = OxmlElement(tag)
    t.text = text or ''
    if text and (text[0] in (' ', '\t') or text[-1] in (' ', '\t')):
        t.set('{http://www.w3.org/XML/1998/namespace}space', 'preserve')
    return t

def _make_run(text):
    r = OxmlElement('w:r')
    r.append(_make_t(text))
    return r

def _make_para_el(text, style_val):
    new_p = OxmlElement('w:p')
    pPr = OxmlElement('w:pPr')
    pStyle = OxmlElement('w:pStyle')
    pStyle.set(qn('w:val'), style_val)
    pPr.append(pStyle)
    new_p.append(pPr)
    new_p.append(_make_run(text))
    return new_p


# ── Section mapping ───────────────────────────────────────────────────────────

def map_sections(doc, clause_numbers):
    """
    Print and return paragraphs belonging to the given clause numbers.
    Returns dict: {clause: [(index, para), ...]}
    """
    results = {c: [] for c in clause_numbers}
    in_section = None

    for i, para in enumerate(doc.paragraphs):
        text  = para.text.strip()
        style = para.style.name if para.style else 'Normal'

        matched = False
        for clause in clause_numbers:
            if clause in text and ('Heading' in style or 'heading' in style.lower()):
                in_section = clause
                print(f'\n=== [{i}] SECTION {clause} | style={style!r} ===')
                print(f'  [{i}] "{text}"')
                results[clause].append((i, para))
                matched = True
                break

        if not matched and in_section:
            if 'Heading' in style and text:
                print(f'  --- end at [{i}] ({style})')
                in_section = None
            elif text:
                print(f'  [{i}] style={style!r:16s} | "{text[:90]}"')
                results[in_section].append((i, para))

    return results


def get_bullet_style_val(doc, fallback='B1'):
    for para in doc.paragraphs:
        pPr = para._element.find(qn('w:pPr'))
        if pPr is not None:
            pStyle = pPr.find(qn('w:pStyle'))
            if pStyle is not None:
                val = pStyle.get(qn('w:val'), '')
                if val.startswith('B') and val[1:].isdigit():
                    return val
    return fallback

def get_style_val(para):
    pPr = para._element.find(qn('w:pPr'))
    if pPr is not None:
        pStyle = pPr.find(qn('w:pStyle'))
        if pStyle is not None:
            return pStyle.get(qn('w:val'))
    return 'Normal'


# ══════════════════════════════════════════════════════════════════════════════
# DIRECT EDIT MODE (no track changes)
# ══════════════════════════════════════════════════════════════════════════════

def delete_para(para):
    """Remove a paragraph from the document entirely."""
    el = para._element
    el.getparent().remove(el)

def insert_para_after(ref_para, text, style_val='Normal'):
    """Insert one paragraph after ref_para. Returns the new element."""
    new_p = _make_para_el(text, style_val)
    ref_para._element.addnext(new_p)
    return new_p

def insert_paras_after(ref_para, items, style_val='Normal'):
    """
    Insert multiple paragraphs in order after ref_para using a moving pointer.
    items: list of str, or list of (text, style_val) tuples.
    Returns the last inserted element.
    """
    ref_el = ref_para._element
    for item in items:
        text, sv = item if isinstance(item, tuple) else (item, style_val)
        new_p = _make_para_el(text, sv)
        ref_el.addnext(new_p)
        ref_el = new_p
    return ref_el

def modify_para_text(para, old_text, new_text):
    """Replace old_text with new_text in a paragraph (collapses all runs)."""
    full = para.text
    if old_text not in full:
        raise ValueError(f"Not found: {old_text!r}\nIn: {full!r}")
    updated = full.replace(old_text, new_text)
    p_el = para._element
    for r in p_el.findall(qn('w:r')):
        p_el.remove(r)
    p_el.append(_make_run(updated))
    return updated


# ══════════════════════════════════════════════════════════════════════════════
# TRACKED CHANGE MODE (review / redline mode)
# ══════════════════════════════════════════════════════════════════════════════

def _ins_attr(rev, author, date):
    return {qn('w:id'): rev.next(), qn('w:author'): author, qn('w:date'): date}

def _del_attr(rev, author, date):
    return {qn('w:id'): rev.next(), qn('w:author'): author, qn('w:date'): date}


def tracked_insert_para_after(ref_para_or_el, text, style_val, rev,
                               author=AUTHOR, date=DATE):
    """
    Insert a new paragraph after ref_para_or_el with tracked insertion marks.
    Word will show it as an insertion in review mode.
    Returns the new XML element (use as next ref for chained inserts).
    """
    new_p = OxmlElement('w:p')

    # Paragraph properties: mark the paragraph mark itself as inserted
    pPr = OxmlElement('w:pPr')
    pStyle = OxmlElement('w:pStyle')
    pStyle.set(qn('w:val'), style_val)
    pPr.append(pStyle)
    rPr = OxmlElement('w:rPr')
    ins_mark = OxmlElement('w:ins')
    for k, v in _ins_attr(rev, author, date).items():
        ins_mark.set(k, v)
    rPr.append(ins_mark)
    pPr.append(rPr)
    new_p.append(pPr)

    # Content wrapped in <w:ins>
    ins = OxmlElement('w:ins')
    for k, v in _ins_attr(rev, author, date).items():
        ins.set(k, v)
    ins.append(_make_run(text))
    new_p.append(ins)

    ref_el = ref_para_or_el if not hasattr(ref_para_or_el, '_element') else ref_para_or_el._element
    ref_el.addnext(new_p)
    return new_p


def tracked_insert_paras_after(ref_para, items, rev, author=AUTHOR, date=DATE):
    """
    Insert multiple paragraphs in order with tracked insertion marks.
    items: list of str, or list of (text, style_val) tuples.
    Uses a moving pointer — order is preserved.
    Returns the last inserted element.
    """
    ref_el = ref_para._element
    for item in items:
        text, sv = item if isinstance(item, tuple) else (item, 'Normal')
        new_p_el = tracked_insert_para_after(ref_el, text, sv, rev, author, date)
        ref_el = new_p_el
    return ref_el


def tracked_delete_para(para, rev, author=AUTHOR, date=DATE):
    """
    Mark a paragraph as deleted using tracked change marks.
    The paragraph stays in the document but Word shows it as struck-through red.
    """
    p_el = para._element

    # Mark the paragraph mark as deleted (in pPr > rPr)
    pPr = p_el.find(qn('w:pPr'))
    if pPr is None:
        pPr = OxmlElement('w:pPr')
        p_el.insert(0, pPr)
    rPr = pPr.find(qn('w:rPr'))
    if rPr is None:
        rPr = OxmlElement('w:rPr')
        pPr.append(rPr)
    del_mark = OxmlElement('w:del')
    for k, v in _del_attr(rev, author, date).items():
        del_mark.set(k, v)
    rPr.append(del_mark)

    # Wrap every run in <w:del> and change <w:t> → <w:delText>
    runs = list(p_el.findall(qn('w:r')))
    for r in runs:
        idx = list(p_el).index(r)
        for t_el in r.findall(qn('w:t')):
            del_t = _make_t(t_el.text, 'w:delText')
            r.remove(t_el)
            r.append(del_t)
        del_wrap = OxmlElement('w:del')
        for k, v in _del_attr(rev, author, date).items():
            del_wrap.set(k, v)
        p_el.remove(r)
        del_wrap.append(r)
        p_el.insert(idx, del_wrap)


def tracked_modify_para(para, old_text, new_text, rev, author=AUTHOR, date=DATE):
    """
    Replace old_text with new_text using tracked del+ins marks.
    Splits the paragraph into: [before][<w:del>old</w:del>][<w:ins>new</w:ins>][after]
    Word shows the old text struck through and new text underlined.
    """
    full = para.text
    if old_text not in full:
        raise ValueError(f"Not found: {old_text!r}\nIn: {full!r}")

    before, _, after = full.partition(old_text)
    p_el = para._element

    # Remove all existing runs
    for r in p_el.findall(qn('w:r')):
        p_el.remove(r)

    # Before (unchanged)
    if before:
        p_el.append(_make_run(before))

    # Tracked deletion of old text
    del_el = OxmlElement('w:del')
    for k, v in _del_attr(rev, author, date).items():
        del_el.set(k, v)
    r_del = OxmlElement('w:r')
    r_del.append(_make_t(old_text, 'w:delText'))
    del_el.append(r_del)
    p_el.append(del_el)

    # Tracked insertion of new text
    ins_el = OxmlElement('w:ins')
    for k, v in _ins_attr(rev, author, date).items():
        ins_el.set(k, v)
    ins_el.append(_make_run(new_text))
    p_el.append(ins_el)

    # After (unchanged)
    if after:
        p_el.append(_make_run(after))


def _char_diff(old, new):
    """
    Return a list of (op, text) tuples for a minimal character-level diff.
    op is one of 'keep', 'del', 'ins'.

    Strategy: first tokenize into digit-runs, letter-runs, and single separator
    characters so that separators like '-' or '.' are kept intact as their own
    tokens; then match tokens with SequenceMatcher; finally apply char-level diff
    within each replaced token pair for maximum granularity.

    Examples:
      ('V18.2.0', 'V18.3.0') →
        [('keep','V18.'), ('del','2'), ('ins','3'), ('keep','.0')]
      ('(2024-11)', '(2026-04)') →
        [('keep','(202'), ('del','4'), ('ins','6'), ('keep','-'),
         ('del','11'), ('ins','04'), ('keep',')')]
    """
    old_tokens = re.findall(r'\d+|[A-Za-z]+|.', old)
    new_tokens = re.findall(r'\d+|[A-Za-z]+|.', new)

    ops = []
    matcher = difflib.SequenceMatcher(None, old_tokens, new_tokens, autojunk=False)
    for tag, i1, i2, j1, j2 in matcher.get_opcodes():
        old_span = ''.join(old_tokens[i1:i2])
        new_span = ''.join(new_tokens[j1:j2])
        if tag == 'equal':
            ops.append(('keep', old_span))
        elif tag == 'replace':
            # Within each replaced token span, apply char-level diff for finer granularity
            cmatcher = difflib.SequenceMatcher(None, old_span, new_span, autojunk=False)
            for ctag, ci1, ci2, cj1, cj2 in cmatcher.get_opcodes():
                if ctag == 'equal':
                    ops.append(('keep', old_span[ci1:ci2]))
                elif ctag == 'replace':
                    ops.append(('del', old_span[ci1:ci2]))
                    ops.append(('ins', new_span[cj1:cj2]))
                elif ctag == 'delete':
                    ops.append(('del', old_span[ci1:ci2]))
                elif ctag == 'insert':
                    ops.append(('ins', new_span[cj1:cj2]))
        elif tag == 'delete':
            ops.append(('del', old_span))
        elif tag == 'insert':
            ops.append(('ins', new_span))
    return ops


def tracked_modify_para_multi(para, replacements, rev, author=AUTHOR, date=DATE):
    """
    Apply multiple tracked del+ins replacements in a single paragraph pass.
    replacements: list of (old_text, new_text) tuples, applied in order of appearance.
    Each replacement uses character-level diff so only the minimally changed characters
    are marked as del/ins, with common characters kept as plain runs in between.
    Use this instead of calling tracked_modify_para twice (which would corrupt the XML).
    """
    full = para.text
    for old_text, _ in replacements:
        if old_text not in full:
            raise ValueError(f"Not found: {old_text!r}\nIn: {full!r}")

    p_el = para._element

    # Remove all existing runs
    for r in p_el.findall(qn('w:r')):
        p_el.remove(r)

    # Walk through the full text, emitting plain runs and char-level del+ins ops
    remaining = full
    for old_text, new_text in replacements:
        idx = remaining.find(old_text)
        if idx == -1:
            continue
        before = remaining[:idx]
        remaining = remaining[idx + len(old_text):]

        if before:
            p_el.append(_make_run(before))

        for op, text in _char_diff(old_text, new_text):
            if op == 'keep':
                p_el.append(_make_run(text))
            elif op == 'del':
                del_el = OxmlElement('w:del')
                for k, v in _del_attr(rev, author, date).items():
                    del_el.set(k, v)
                r_del = OxmlElement('w:r')
                r_del.append(_make_t(text, 'w:delText'))
                del_el.append(r_del)
                p_el.append(del_el)
            elif op == 'ins':
                ins_el = OxmlElement('w:ins')
                for k, v in _ins_attr(rev, author, date).items():
                    ins_el.set(k, v)
                ins_el.append(_make_run(text))
                p_el.append(ins_el)

    # Emit any trailing text
    if remaining:
        p_el.append(_make_run(remaining))


def tracked_insert_table_row(tbl, cell_texts, rev, author=AUTHOR, date=DATE):
    """
    Insert a new row immediately after the last non-empty row in tbl, as a
    tracked insertion.  Empty pre-allocated rows at the table bottom are skipped
    so the new content appears directly under the previous entry.

    The new row is deep-copied from the last content row so that ALL formatting
    (cell widths, borders, shading, paragraph style, run font/size) is inherited —
    exactly as clicking "Insert Row Below" does in Word.

    tbl: python-docx Table object
    cell_texts: list of strings, one per column
    """
    tbl_el = tbl._tbl
    all_trs = tbl_el.findall(qn('w:tr'))

    # Find the last row that contains at least one non-empty <w:t> node.
    # This skips pre-allocated blank rows at the table bottom.
    _CONTENT_TAGS = {qn('w:t'), qn('w:hyperlink'), qn('w:drawing'), qn('w:object')}
    last_content_tr = all_trs[-1]
    for tr in reversed(all_trs):
        has_text  = any(t.text and t.text.strip() for t in tr.findall('.//' + qn('w:t')))
        has_other = any(el.tag in _CONTENT_TAGS for el in tr.iter())
        if has_text or has_other:
            last_content_tr = tr
            break

    # Deep-copy the last content row — inherits all cell/paragraph/run formatting.
    new_tr = copy.deepcopy(last_content_tr)

    # Mark the row itself as a tracked insertion in <w:trPr>.
    trPr = new_tr.find(qn('w:trPr'))
    if trPr is None:
        trPr = OxmlElement('w:trPr')
        new_tr.insert(0, trPr)
    for child in list(trPr):
        if child.tag == qn('w:ins'):
            trPr.remove(child)
    tr_ins = OxmlElement('w:ins')
    for k, v in _ins_attr(rev, author, date).items():
        tr_ins.set(k, v)
    trPr.append(tr_ins)

    # For each cell: extract the existing run's rPr, clear text content, insert new text.
    cells_in_new_tr = new_tr.findall(qn('w:tc'))
    for i, tc in enumerate(cells_in_new_tr):
        p = tc.find('.//' + qn('w:p'))
        if p is None:
            continue

        # Capture the first run's rPr (font size, bold, etc.) before clearing.
        first_run_rpr = None
        for r in list(p.iter(qn('w:r'))):
            rpr = r.find(qn('w:rPr'))
            if rpr is not None:
                first_run_rpr = copy.deepcopy(rpr)
            break

        # Remove all non-pPr children (runs, ins, del, hyperlinks, etc.)
        for child in list(p):
            if child.tag != qn('w:pPr'):
                p.remove(child)

        # Ensure pPr exists with a paragraph-mark ins tracking element.
        pPr = p.find(qn('w:pPr'))
        if pPr is None:
            pPr = OxmlElement('w:pPr')
            p.insert(0, pPr)
        rPr = pPr.find(qn('w:rPr'))
        if rPr is None:
            rPr = OxmlElement('w:rPr')
            pPr.append(rPr)
        for child in list(rPr):
            if child.tag == qn('w:ins'):
                rPr.remove(child)
        p_ins_mark = OxmlElement('w:ins')
        for k, v in _ins_attr(rev, author, date).items():
            p_ins_mark.set(k, v)
        rPr.append(p_ins_mark)

        # Build new run, re-using the inherited rPr so font size / style matches.
        r_new = OxmlElement('w:r')
        if first_run_rpr is not None:
            r_new.append(first_run_rpr)
        text = cell_texts[i] if i < len(cell_texts) else ''
        r_new.append(_make_t(text))

        # Wrap the run in a tracked-insertion element.
        ins_el = OxmlElement('w:ins')
        for k, v in _ins_attr(rev, author, date).items():
            ins_el.set(k, v)
        ins_el.append(r_new)
        p.append(ins_el)

    last_content_tr.addnext(new_tr)