from __future__ import annotations

import hashlib
from pathlib import Path
from typing import Any

import yaml
from django.conf import settings


DEFAULT_CONFIG_PATH = (
    Path(settings.BASE_DIR)
    / "review_agent"
    / "application_form_fill"
    / "templates"
    / "application_form_templates_v1.yaml"
)

SUPPORTED_TARGET_TYPES = {"table_row", "placeholder"}
SUPPORTED_FILE_FORMATS = {"doc", "docx"}


def load_template_config(path: str | Path | None = None) -> dict[str, Any]:
    config_path = Path(path) if path else DEFAULT_CONFIG_PATH
    with config_path.open("r", encoding="utf-8") as handle:
        payload = yaml.safe_load(handle) or {}
    return payload


def compute_config_hash(path: str | Path | None = None) -> str:
    config_path = Path(path) if path else DEFAULT_CONFIG_PATH
    digest = hashlib.sha256()
    with config_path.open("rb") as handle:
        for chunk in iter(lambda: handle.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def validate_template_config(config: dict[str, Any], *, base_dir: str | Path | None = None) -> list[str]:
    errors: list[str] = []
    root = Path(base_dir) if base_dir else Path(settings.BASE_DIR)

    version = config.get("version")
    if not version:
        errors.append("模板配置缺少 version。")

    source_dir_value = config.get("source_dir")
    source_dir = root / source_dir_value if source_dir_value else None
    if not source_dir_value:
        errors.append("模板配置缺少 source_dir。")
    elif not source_dir.exists():
        errors.append(f"模板 source_dir 不存在：{source_dir_value}")

    templates = config.get("templates")
    if not isinstance(templates, list) or not templates:
        errors.append("模板配置必须包含非空 templates 列表。")
        return errors

    seen_codes: set[str] = set()
    for index, template in enumerate(templates, start=1):
        if not isinstance(template, dict):
            errors.append(f"第 {index} 个模板配置必须是对象。")
            continue
        code = str(template.get("code") or "").strip()
        if not code:
            errors.append(f"第 {index} 个模板缺少 code。")
        elif code in seen_codes:
            errors.append(f"模板 code 重复：{code}")
        seen_codes.add(code)

        file_format = str(template.get("file_format") or "").strip().lower()
        if file_format not in SUPPORTED_FILE_FORMATS:
            errors.append(f"模板 {code or index} 的 file_format 不支持：{file_format or '空'}")

        source_file = str(template.get("source_file") or "").strip()
        if not source_file:
            errors.append(f"模板 {code or index} 缺少 source_file。")
        elif source_dir and source_dir.exists() and not (source_dir / source_file).exists():
            errors.append(f"模板 {code or index} 的 source_file 不存在：{source_file}")

        fields = template.get("fields") or []
        if not isinstance(fields, list):
            errors.append(f"模板 {code or index} 的 fields 必须是列表。")
            continue
        for field_index, field in enumerate(fields, start=1):
            target = field.get("target") if isinstance(field, dict) else None
            target_type = str((target or {}).get("type") or "").strip()
            if target_type not in SUPPORTED_TARGET_TYPES:
                errors.append(
                    f"模板 {code or index} 第 {field_index} 个字段 target.type 不支持：{target_type or '空'}"
                )
    return errors


def template_specs(config: dict[str, Any]) -> list[dict[str, Any]]:
    return list(config.get("templates") or [])