from rest_framework import serializers

from .models import (
    AITask,
    CreationConversation,
    CreationMessage,
    ImageConversation,
    ModelConfig,
    ModelProvider,
)


class ModelProviderSerializer(serializers.ModelSerializer):
    class Meta:
        model = ModelProvider
        fields = ["id", "name", "display_name", "status", "base_url", "metadata"]
        read_only_fields = fields


class ModelConfigSerializer(serializers.ModelSerializer):
    provider = ModelProviderSerializer(read_only=True)

    class Meta:
        model = ModelConfig
        fields = ["id", "provider", "name", "display_name", "capability", "endpoint", "unit_price", "status", "metadata"]
        read_only_fields = fields


class ImageConversationSerializer(serializers.ModelSerializer):
    """图片创作对话:左栏列表用。title 可写(重命名),mode/product 创建时可指定。"""

    task_count = serializers.SerializerMethodField()

    class Meta:
        model = ImageConversation
        fields = [
            "id", "title", "mode", "product", "task_count",
            "is_deleted", "purged_at", "last_active_at", "created_at", "updated_at",
        ]
        read_only_fields = ["id", "task_count", "is_deleted", "purged_at", "last_active_at", "created_at", "updated_at"]

    def get_task_count(self, obj) -> int:
        # list 接口已 annotate;无 annotate 时回落实时 count(详情/创建场景)
        cached = getattr(obj, "_task_count", None)
        return cached if cached is not None else obj.tasks.count()


class ImageConversationTrashSerializer(ImageConversationSerializer):
    """垃圾桶专用对话契约：只额外暴露一张展示封面，不影响普通对话列表查询。"""

    cover_preview_url = serializers.SerializerMethodField()

    class Meta(ImageConversationSerializer.Meta):
        fields = [*ImageConversationSerializer.Meta.fields, "cover_preview_url"]
        read_only_fields = [*ImageConversationSerializer.Meta.read_only_fields, "cover_preview_url"]

    def get_cover_preview_url(self, obj) -> str:
        return str(getattr(obj, "_trash_cover_preview_url", "") or "")


class AITaskSerializer(serializers.ModelSerializer):
    model_config = ModelConfigSerializer(read_only=True)
    # 从 request_payload 抽出的分组/标签信息(由 AITaskViewSet annotate 提供;其它调用处无此注解则为 None)。
    # 不直接读 obj.request_payload —— 那列已 defer,读了会触发懒加载把几 MB payload 整列拉回。
    batch_id = serializers.SerializerMethodField()
    mode = serializers.SerializerMethodField()

    def get_batch_id(self, obj):
        return getattr(obj, "rp_batch_id", None)

    def get_mode(self, obj):
        return getattr(obj, "rp_mode", None)

    class Meta:
        model = AITask
        fields = [
            "id",
            "project",
            "task_type",
            "batch_id",
            "mode",
            "status",
            "model_config",
            "provider_task_id",
            "estimated_cost",
            "actual_cost",
            "error_code",
            "error_message",
            "submitted_at",
            "completed_at",
            "is_deleted",
            "purged_at",
            "created_at",
            "updated_at",
        ]
        # batch_id / mode 是显式声明的 SerializerMethodField(本就只读),不能再列进 read_only_fields(DRF 会报错)
        read_only_fields = [f for f in fields if f not in ("batch_id", "mode")]



class CreationMessageSerializer(serializers.ModelSerializer):
    """全能创作对话流里的一条消息。前端**按 kind 分发到不同卡片组件**,
    结构化内容一律在 payload 里(契约 §2),不要从 text 里解析。"""

    class Meta:
        model = CreationMessage
        fields = ["id", "role", "kind", "text", "payload", "refs", "task", "seq", "created_at"]
        read_only_fields = fields


class CreationConversationSerializer(serializers.ModelSerializer):
    """会话列表 / 详情。title 可写(重命名);params 创建后也可改(对话页改模型/比例后立刻生效);
    mode 创建后不可改。"""

    message_count = serializers.SerializerMethodField()
    cover_url = serializers.SerializerMethodField()

    class Meta:
        model = CreationConversation
        fields = [
            "id", "title", "mode", "preset", "params", "status",
            "message_count", "cover_url",
            "last_active_at", "created_at", "updated_at",
        ]
        read_only_fields = [
            "id", "status", "message_count", "cover_url",
            "last_active_at", "created_at", "updated_at",
        ]

    def get_message_count(self, obj) -> int:
        cached = getattr(obj, "_message_count", None)
        return cached if cached is not None else obj.messages.count()

    def get_cover_url(self, obj) -> str:
        """历史页封面 = **最新一版**结果(重生成是往下叠加,所以取最后一条 RESULT)。"""
        last = (
            obj.messages.filter(kind=CreationMessage.Kind.RESULT)
            .order_by("-seq")
            .values_list("payload", flat=True)
            .first()
        )
        if not last:
            return ""
        assets = (last or {}).get("assets") or []
        if not assets:
            return ""
        first = assets[0] or {}
        return first.get("cover") or first.get("url") or ""

    def update(self, instance, validated_data):
        # mode 定死:允许传但忽略,避免前端误改后顶栏参数与已生成内容对不上
        validated_data.pop("mode", None)
        return super().update(instance, validated_data)


class CreationConversationDetailSerializer(CreationConversationSerializer):
    """详情:带全量消息,进对话页一次性回填。"""

    messages = CreationMessageSerializer(many=True, read_only=True)
    pinned_refs = serializers.JSONField(read_only=True)

    class Meta(CreationConversationSerializer.Meta):
        fields = [*CreationConversationSerializer.Meta.fields, "messages", "pinned_refs"]
        read_only_fields = [
            *CreationConversationSerializer.Meta.read_only_fields, "messages", "pinned_refs",
        ]