#!/usr/bin/env python3
# -*- coding: utf-8 -*-
from __future__ import annotations

from dataclasses import dataclass
from typing import Any, Iterable, List, Optional, Tuple
from urllib.parse import unquote_plus

from . import constants as C


@dataclass
class ThreatResult:
    threat_type: str
    score: int
    field_name: str
    rule: str = ""
    matched: str = ""
    value_preview: str = ""

    def to_dict(self) -> dict:
        return {
            "threat_type": self.threat_type,
            "score": int(self.score),
            "field_name": self.field_name,
            "rule": self.rule,
            "matched": self.matched,
            "value_preview": self.value_preview,
        }


class ThreatDetector:
    def __init__(
        self,
        *,
        max_value_length: int = 4096,
        max_decode_rounds: int = 2,
    ) -> None:
        self.max_value_length = max(64, int(max_value_length))
        self.max_decode_rounds = max(0, int(max_decode_rounds))

    def scan_input(self, value: Any, field_name: str = "value") -> List[ThreatResult]:
        """扫描单个输入值（支持 dict/list 等嵌套结构）。"""
        results: List[ThreatResult] = []
        for sub_field, leaf in self._flatten_value(value, field_name):
            text = self._stringify(leaf)
            if not text:
                continue
            if len(text) > self.max_value_length:
                text = text[: self.max_value_length]
            results.extend(self._scan_text(text, sub_field))
        results.sort(key=lambda r: int(r.score), reverse=True)
        return results

    def scan_request(self, request: Any) -> List[ThreatResult]:
        """扫描整个请求对象（兼容 Flask Request / dict 风格对象）。"""
        results: List[ThreatResult] = []
        for field_name, value in self._extract_request_fields(request):
            results.extend(self.scan_input(value, field_name))
        results.sort(key=lambda r: int(r.score), reverse=True)
        return results

    # ==================== Internal scanning ====================

    def _scan_text(self, text: str, field_name: str) -> List[ThreatResult]:
        hits: List[ThreatResult] = []

        for check in [
            self._check_jndi_injection,
            self._check_sql_injection,
            self._check_xss,
            self._check_path_traversal,
            self._check_command_injection,
        ]:
            result = check(text)
            if result:
                threat_type, score, rule, matched = result
                hits.append(
                    ThreatResult(
                        threat_type=threat_type,
                        score=int(score),
                        field_name=field_name,
                        rule=rule,
                        matched=matched,
                        value_preview=self._preview(text),
                    )
                )

        return hits

    def _check_jndi_injection(self, text: str) -> Optional[Tuple[str, int, str, str]]:
        # 1) Direct match
        m = C.JNDI_DIRECT_RE.search(text)
        if m:
            return (C.THREAT_TYPE_JNDI_INJECTION, C.SCORE_JNDI_DIRECT, "JNDI_DIRECT", m.group(0))

        # 2) URL-decoded
        decoded = self._multi_unquote(text)
        if decoded != text:
            m2 = C.JNDI_DIRECT_RE.search(decoded)
            if m2:
                return (C.THREAT_TYPE_JNDI_INJECTION, C.SCORE_JNDI_DIRECT, "JNDI_DIRECT_URL_DECODED", m2.group(0))

        # 3) Obfuscation patterns (raw/decoded)
        for candidate, rule in [(text, "JNDI_OBFUSCATED"), (decoded, "JNDI_OBFUSCATED_URL_DECODED")]:
            m3 = C.JNDI_OBFUSCATED_RE.search(candidate)
            if m3:
                return (C.THREAT_TYPE_JNDI_INJECTION, C.SCORE_JNDI_OBFUSCATED, rule, m3.group(0))

        # 4) Try limited de-obfuscation to reveal ${jndi:...}
        deobf = self._deobfuscate_log4j(decoded)
        if deobf and deobf != decoded:
            m4 = C.JNDI_DIRECT_RE.search(deobf)
            if m4:
                return (C.THREAT_TYPE_JNDI_INJECTION, C.SCORE_JNDI_OBFUSCATED, "JNDI_DEOBFUSCATED", m4.group(0))

        # 5) Nested expression heuristic
        for candidate in [text, decoded]:
            m5 = C.NESTED_EXPRESSION_RE.search(candidate)
            if m5:
                return (C.THREAT_TYPE_NESTED_EXPRESSION, C.SCORE_NESTED_EXPRESSION, "NESTED_EXPRESSION", m5.group(0))

        return None

    def _check_sql_injection(self, text: str) -> Optional[Tuple[str, int, str, str]]:
        candidates = [text, self._multi_unquote(text)]
        for candidate in candidates:
            m = C.SQLI_UNION_SELECT_RE.search(candidate)
            if m:
                return (C.THREAT_TYPE_SQL_INJECTION, C.SCORE_SQL_INJECTION, "SQLI_UNION_SELECT", m.group(0))
            m = C.SQLI_OR_1_EQ_1_RE.search(candidate)
            if m:
                return (C.THREAT_TYPE_SQL_INJECTION, C.SCORE_SQL_INJECTION, "SQLI_OR_1_EQ_1", m.group(0))
        return None

    def _check_xss(self, text: str) -> Optional[Tuple[str, int, str, str]]:
        candidates = [text, self._multi_unquote(text)]
        for candidate in candidates:
            m = C.XSS_SCRIPT_TAG_RE.search(candidate)
            if m:
                return (C.THREAT_TYPE_XSS, C.SCORE_XSS, "XSS_SCRIPT_TAG", m.group(0))
            m = C.XSS_JS_PROTOCOL_RE.search(candidate)
            if m:
                return (C.THREAT_TYPE_XSS, C.SCORE_XSS, "XSS_JS_PROTOCOL", m.group(0))
            m = C.XSS_INLINE_EVENT_HANDLER_RE.search(candidate)
            if m:
                return (C.THREAT_TYPE_XSS, C.SCORE_XSS, "XSS_INLINE_EVENT_HANDLER", m.group(0))
        return None

    def _check_path_traversal(self, text: str) -> Optional[Tuple[str, int, str, str]]:
        decoded = self._multi_unquote(text)
        candidates = [text, decoded]
        for candidate in candidates:
            m = C.PATH_TRAVERSAL_RE.search(candidate)
            if m:
                return (C.THREAT_TYPE_PATH_TRAVERSAL, C.SCORE_PATH_TRAVERSAL, "PATH_TRAVERSAL", m.group(0))
        return None

    def _check_command_injection(self, text: str) -> Optional[Tuple[str, int, str, str]]:
        decoded = self._multi_unquote(text)
        candidates = [text, decoded]
        for candidate in candidates:
            m = C.CMD_INJECTION_SUBSHELL_RE.search(candidate)
            if m:
                return (C.THREAT_TYPE_COMMAND_INJECTION, C.SCORE_COMMAND_INJECTION, "CMD_SUBSHELL", m.group(0))
            m = C.CMD_INJECTION_OPERATOR_WITH_CMD_RE.search(candidate)
            if m:
                return (C.THREAT_TYPE_COMMAND_INJECTION, C.SCORE_COMMAND_INJECTION, "CMD_OPERATOR_WITH_CMD", m.group(0))
        return None

    # ==================== Helpers ====================

    def _preview(self, text: str, limit: int = 160) -> str:
        s = text.replace("\n", "\\n").replace("\r", "\\r").replace("\t", "\\t")
        if len(s) <= limit:
            return s
        return s[: limit - 3] + "..."

    def _stringify(self, value: Any) -> str:
        if value is None:
            return ""
        if isinstance(value, bytes):
            try:
                return value.decode("utf-8", errors="ignore")
            except Exception:
                return ""
        try:
            return str(value)
        except Exception:
            return ""

    def _multi_unquote(self, text: str) -> str:
        s = text
        for _ in range(self.max_decode_rounds):
            try:
                nxt = unquote_plus(s)
            except Exception:
                break
            if nxt == s:
                break
            s = nxt
        return s

    def _deobfuscate_log4j(self, text: str) -> str:
        # Replace ${...:-x} with x (including ${::-x}).
        # This is intentionally conservative to reduce false positives.
        import re

        s = text
        pattern = re.compile(r"\$\{[^{}]{0,50}:-([a-zA-Z])\}")
        for _ in range(3):
            nxt = pattern.sub(lambda m: m.group(1), s)
            if nxt == s:
                break
            s = nxt
        return s

    def _flatten_value(self, value: Any, field_name: str) -> Iterable[Tuple[str, Any]]:
        if isinstance(value, dict):
            for k, v in value.items():
                key = self._stringify(k) or "key"
                sub_name = f"{field_name}.{key}" if field_name else key
                yield from self._flatten_value(v, sub_name)
            return
        if isinstance(value, (list, tuple, set)):
            for i, v in enumerate(value):
                sub_name = f"{field_name}[{i}]"
                yield from self._flatten_value(v, sub_name)
            return
        yield (field_name, value)

    def _extract_request_fields(self, request: Any) -> List[Tuple[str, Any]]:
        # dict-like input (useful for unit tests / non-Flask callers)
        if isinstance(request, dict):
            out: List[Tuple[str, Any]] = []
            for k, v in request.items():
                out.append((self._stringify(k) or "request", v))
            return out

        out: List[Tuple[str, Any]] = []

        # path / method
        for attr_name in ["method", "path", "full_path", "url", "remote_addr"]:
            try:
                v = getattr(request, attr_name, None)
            except Exception:
                v = None
            if v:
                out.append((attr_name, v))

        # args / form (Flask MultiDict)
        out.extend(self._extract_multidict(getattr(request, "args", None), "args"))
        out.extend(self._extract_multidict(getattr(request, "form", None), "form"))

        # headers
        try:
            headers = getattr(request, "headers", None)
            if headers is not None:
                try:
                    items = headers.items()
                except Exception:
                    items = []
                for k, v in items:
                    out.append((f"headers.{self._stringify(k)}", v))
        except Exception:
            pass

        # cookies
        try:
            cookies = getattr(request, "cookies", None)
            if isinstance(cookies, dict):
                for k, v in cookies.items():
                    out.append((f"cookies.{self._stringify(k)}", v))
        except Exception:
            pass

        # json body
        data = None
        try:
            get_json = getattr(request, "get_json", None)
            if callable(get_json):
                data = get_json(silent=True)
        except Exception:
            data = None

        if data is not None:
            for name, v in self._flatten_value(data, "json"):
                out.append((name, v))
            return out

        # raw body (as a fallback)
        try:
            get_data = getattr(request, "get_data", None)
            if callable(get_data):
                raw = get_data(cache=True, as_text=True)
                if raw:
                    out.append(("body", raw))
        except Exception:
            pass

        return out

    def _extract_multidict(self, md: Any, prefix: str) -> List[Tuple[str, Any]]:
        out: List[Tuple[str, Any]] = []
        if md is None:
            return out
        try:
            items = md.items(multi=True)
        except Exception:
            try:
                items = md.items()
            except Exception:
                return out
        for k, v in items:
            out.append((f"{prefix}.{self._stringify(k)}", v))
        return out