from __future__ import annotations

from datetime import datetime
from typing import Literal
from uuid import UUID

from pydantic import BaseModel, ConfigDict, Field, computed_field, field_validator


TaskStatus = Literal["backlog", "in_progress", "done"]


class ErrorDTO(BaseModel):
    error: str = Field(..., examples=["invalid_id"])
    message: str = Field(..., examples=["Task was not found"])


class TaskCreateDTO(BaseModel):
    model_config = ConfigDict(extra="forbid")

    title: str = Field(
        ...,
        min_length=1,
        max_length=100,
        description="Task title",
        examples=["Implement CSV export"],
    )

    @field_validator("title")
    @classmethod
    def validate_title(cls, value: str) -> str:
        value = value.strip()
        if not value:
            raise ValueError("Title must not be empty")
        return value


class TaskUpdateDTO(BaseModel):
    model_config = ConfigDict(extra="forbid")

    title: str | None = Field(
        default=None,
        min_length=1,
        max_length=100,
        description="Updated task title",
        examples=["Fix workflow metrics"],
    )

    @field_validator("title")
    @classmethod
    def validate_title(cls, value: str | None) -> str | None:
        if value is None:
            return None

        value = value.strip()
        if not value:
            raise ValueError("Title must not be empty")
        return value


class TaskDTO(BaseModel):
    model_config = ConfigDict(
        extra="forbid",
        frozen=True,
        populate_by_name=True,
    )

    id: UUID
    title: str = Field(..., min_length=1, max_length=100)
    created_at: datetime
    started_at: datetime | None = None
    done_at: datetime | None = None

    @computed_field(return_type=str)
    @property
    def status(self) -> TaskStatus:
        if self.done_at is not None:
            return "done"
        if self.started_at is not None:
            return "in_progress"
        return "backlog"


class TaskListItemDTO(BaseModel):
    model_config = ConfigDict(
        extra="forbid",
        frozen=True,
        populate_by_name=True,
    )

    id: UUID
    title: str = Field(..., min_length=1, max_length=100)
    created_at: datetime
    started_at: datetime | None = None
    done_at: datetime | None = None

    @computed_field(return_type=str)
    @property
    def status(self) -> TaskStatus:
        if self.done_at is not None:
            return "done"
        if self.started_at is not None:
            return "in_progress"
        return "backlog"


class TaskListDTO(BaseModel):
    model_config = ConfigDict(extra="forbid", frozen=True)

    items: list[TaskListItemDTO]
    total: int = Field(..., ge=0)
    limit: int = Field(..., ge=1, le=1000)
    offset: int = Field(..., ge=0)


class TaskQueryDTO(BaseModel):
    model_config = ConfigDict(extra="forbid")

    limit: int = Field(default=100, ge=1, le=1000)
    offset: int = Field(default=0, ge=0)
    status: TaskStatus | None = Field(default=None)
    search: str | None = Field(default=None, max_length=100)

    @field_validator("search")
    @classmethod
    def normalize_search(cls, value: str | None) -> str | None:
        if value is None:
            return None

        value = value.strip()
        return value or None


class TaskExportRowDTO(BaseModel):
    model_config = ConfigDict(extra="forbid", frozen=True)

    id: UUID
    title: str
    status: TaskStatus
    created_at: datetime
    started_at: datetime | None = None
    done_at: datetime | None = None


class TaskBoardItemDTO(BaseModel):
    model_config = ConfigDict(extra="forbid", frozen=True)

    id: UUID
    title: str = Field(..., min_length=1, max_length=100)
    status: TaskStatus
    display_date_label: str = Field(..., min_length=1, max_length=20)
    display_date_value: datetime | None = None


class TaskBoardDTO(BaseModel):
    model_config = ConfigDict(extra="forbid", frozen=True)

    backlog_tasks: list[TaskBoardItemDTO]
    in_progress_tasks: list[TaskBoardItemDTO]
    done_tasks: list[TaskBoardItemDTO]


class TaskDetailsDTO(BaseModel):
    model_config = ConfigDict(extra="forbid", frozen=True)

    id: UUID
    title: str = Field(..., min_length=1, max_length=100)
    status: TaskStatus
    created_at: datetime
    started_at: datetime | None = None
    done_at: datetime | None = None
    cycle_time: str