import re
from typing import Any, Dict, List, Tuple
import unicodedata

SPAN_RE = re.compile(r"<span>(.*?)</span>")

_ALLOWED_EMOJI_GLUE = {
    "\u200d",  # ZWJ
    "\ufe0f",  # variation selector-16
    "\u20e3",  # combining enclosing keycap
}

def validate_emoji_only(value: str) -> Tuple[bool, str]:
    if not isinstance(value, str) or not value.strip():
        return False, "empty emoji string"

    s = value.strip()

    for ch in s:
        if unicodedata.category(ch).startswith("L"):
            return False, f"contains letters: {repr(ch)}"

    try:
        import emoji
    except ImportError:
        return False, "missing dependency: pip install emoji"

    tokens = emoji.emoji_list(s)
    if not tokens:
        return False, "no emoji found"

    covered = [False] * len(s)

    for t in tokens:
        start, end = t["match_start"], t["match_end"]
        for i in range(start, end):
            covered[i] = True

    for i, ch in enumerate(s):
        if covered[i]:
            continue
        if ch in _ALLOWED_EMOJI_GLUE:
            continue
        return False, f"contains non-emoji character: {repr(ch)}"

    return True, "ok"

def extract_marked_spans(marked_sentence: str) -> List[str]:
    return [s.strip() for s in SPAN_RE.findall(marked_sentence)]


def validate_marked_matches_original(marked: str, original: str) -> Tuple[bool, str]:
    stripped = marked.replace("<span>", "").replace("</span>", "")
    if stripped != original:
        # Find first differing character for diagnosis
        for i, (a, b) in enumerate(zip(stripped, original)):
            if a != b:
                ctx_s = repr(stripped[max(0, i-10):i+10])
                ctx_o = repr(original[max(0, i-10):i+10])
                return False, f"char {i}: got {ctx_s}, expected {ctx_o}"
        # One is a prefix of the other
        shorter = "stripped" if len(stripped) < len(original) else "original"
        return False, f"{shorter} is shorter ({len(stripped)} vs {len(original)} chars)"
    return True, "ok"



def validate_marking_json(obj: Dict[str, Any], original_sentence: str) -> Tuple[bool, str]:
    if not isinstance(obj, dict):
        return False, "marking result is not a dict"
    marked = obj.get("marked")
    if not isinstance(marked, str):
        return False, "missing/invalid 'marked' field"
    return validate_marked_matches_original(marked, original_sentence)


def validate_indexed_annotation_json(obj: Dict[str, Any], original: str) -> Tuple[bool, str]:
    """Validate an indexed-format annotation dict against the original sentence.

    Expected shape: {"annotations": [{"start": int, "end": int, "text": str, "emojis": str}, ...]}
    Checks: valid list, each entry has int start/end within bounds, text matches original[start:end],
    emoji-only content, and spans are ordered left-to-right (non-overlapping).
    """
    if not isinstance(obj, dict):
        return False, "annotation is not a dict"
    annotations = obj.get("annotations")
    if not isinstance(annotations, list):
        return False, "missing/invalid 'annotations' field"
    if not annotations:
        return True, "ok"

    prev_end = 0
    for i, item in enumerate(annotations):
        if not isinstance(item, dict):
            return False, f"annotation entry {i} is not a dict"
        start = item.get("start")
        end   = item.get("end")
        text  = item.get("text")
        emojis = item.get("emojis")

        if not isinstance(start, int) or not isinstance(end, int):
            return False, f"annotation entry {i}: start/end must be integers"
        if not (0 <= start < end <= len(original)):
            return False, (
                f"annotation entry {i}: offsets [{start}:{end}] out of range "
                f"for sentence of length {len(original)}"
            )
        if start < prev_end:
            return False, (
                f"annotation entry {i}: spans must be ordered and non-overlapping "
                f"(start={start} < prev_end={prev_end})"
            )
        if not isinstance(text, str):
            return False, f"annotation entry {i}: missing/invalid 'text' field"
        expected_text = original[start:end]
        if text != expected_text:
            return False, (
                f"annotation entry {i}: text {text!r} does not match "
                f"original[{start}:{end}]={expected_text!r}"
            )
        if not isinstance(emojis, str) or not emojis.strip():
            return False, f"annotation entry {i}: empty/missing 'emojis' for span '{text}'"
        ok_emoji, why = validate_emoji_only(emojis.strip())
        if not ok_emoji:
            return False, f"non-emoji content for span '{text}': {why}"

        prev_end = end

    return True, "ok"


def validate_annotation_json(obj: Dict[str, Any], original_sentence: str) -> Tuple[bool, str]:
    if not isinstance(obj, dict):
        return False, "annotation is not a dict"

    marked = obj.get("marked")
    if not isinstance(marked, str):
        return False, "missing/invalid 'marked' field"

    annotations = obj.get("annotations")
    if not isinstance(annotations, list):
        return False, "missing/invalid 'annotations' field"

    # Check that stripping tags recovers the original sentence
    ok, reason = validate_marked_matches_original(marked, original_sentence)
    if not ok:
        return False, reason

    # Extract spans positionally from marked text (one entry per occurrence, in order)
    marked_spans = extract_marked_spans(marked)

    # Zero spans is valid (e.g. all stopwords or named entities)
    if not marked_spans:
        if annotations:
            return False, "annotations list is non-empty but no spans found in marked text"
        return True, "ok"

    # annotations must be a positional list matching marked_spans exactly
    if len(annotations) != len(marked_spans):
        return False, (
            f"annotations length ({len(annotations)}) != "
            f"number of marked spans ({len(marked_spans)})"
        )

    for i, (item, expected_span) in enumerate(zip(annotations, marked_spans)):
        if not isinstance(item, dict):
            return False, f"annotation entry {i} is not a dict"
        span = item.get("span")
        emojis = item.get("emojis")
        if not isinstance(span, str) or not span.strip():
            return False, f"annotation entry {i} has empty/missing 'span'"
        if span.strip() != expected_span:
            return False, (
                f"annotation entry {i} span {span.strip()!r} "
                f"does not match marked span {expected_span!r}"
            )
        if not isinstance(emojis, str) or not emojis.strip():
            return False, f"annotation entry {i} has empty/missing 'emojis' for span: {span}"
        ok_emoji, why = validate_emoji_only(emojis.strip())
        if not ok_emoji:
            return False, f"non-emoji content for span '{span}': {why}"

    return True, "ok"