"""Pydantic schemas for the 工号系统 (employee-number allocation) feature."""

from __future__ import annotations

from datetime import date, datetime
from uuid import UUID

from pydantic import BaseModel, Field, field_validator


class EmployeeNumberCreateRequest(BaseModel):
    """Allocate a single 工号. The number itself is assigned by the
    server — the caller supplies only the descriptive fields."""

    name: str = Field(..., min_length=1, max_length=128)
    hire_date: date | None = None
    remark: str | None = Field(default=None, max_length=255)
    # 一级部门 (BU). Optional; validated against the live BU list server-side.
    bu: str | None = Field(default=None, max_length=128)

    @field_validator("name")
    @classmethod
    def _strip_name(cls, v: str) -> str:
        v = (v or "").strip()
        if not v:
            raise ValueError("name must not be blank")
        return v

    @field_validator("remark", "bu")
    @classmethod
    def _strip_optional(cls, v: str | None) -> str | None:
        if v is None:
            return None
        return v.strip() or None


class EmployeeNumberUpdateRequest(BaseModel):
    """Maintain a single 工号's descriptive fields.

    The number itself (``employee_no`` / ``seq``) is immutable and is NOT
    part of this payload — only the descriptive fields can change. Same
    field set and validation as allocation."""

    name: str = Field(..., min_length=1, max_length=128)
    hire_date: date | None = None
    remark: str | None = Field(default=None, max_length=255)
    bu: str | None = Field(default=None, max_length=128)

    @field_validator("name")
    @classmethod
    def _strip_name(cls, v: str) -> str:
        v = (v or "").strip()
        if not v:
            raise ValueError("name must not be blank")
        return v

    @field_validator("remark", "bu")
    @classmethod
    def _strip_optional(cls, v: str | None) -> str | None:
        if v is None:
            return None
        return v.strip() or None


class EmployeeNumberResponse(BaseModel):
    id: UUID
    employee_no: str
    seq: int | None
    name: str | None
    hire_date: date | None
    remark: str | None
    bu: str | None
    source: str
    created_by: UUID | None
    created_by_name: str | None
    created_at: datetime


class NextNumberResponse(BaseModel):
    """Preview of the number the next allocation will produce."""

    next_employee_no: str
    next_seq: int
    current_max_no: str | None


class SetNextNumberRequest(BaseModel):
    """Manually set the next 工号 the allocator will hand out.

    ``next_employee_no`` may be given padded or not (``P5000`` / ``P05000``);
    it is canonicalised server-side. The target must be strictly greater than
    the current maximum allocated number (a smaller value would collide with
    an existing 工号), so a floor only ever moves the sequence forward.
    """

    next_employee_no: str = Field(..., min_length=1, max_length=16)
    reason: str = Field(..., min_length=1, max_length=500)

    @field_validator("next_employee_no", "reason")
    @classmethod
    def _strip(cls, v: str) -> str:
        v = (v or "").strip()
        if not v:
            raise ValueError("must not be blank")
        return v


class NextNumberOverrideResponse(BaseModel):
    """One 工号-维护 (next-number override) record."""

    id: UUID
    next_employee_no: str
    next_seq: int
    previous_next_employee_no: str | None
    previous_next_seq: int | None
    reason: str
    created_by: UUID | None
    created_by_name: str | None
    created_at: datetime


class ImportErrorRow(BaseModel):
    row: int  # 1-based row number in the uploaded file (data rows, header = row 1)
    employee_no: str | None
    reason: str


class ImportResultResponse(BaseModel):
    total: int
    created: int
    skipped: int
    errors: list[ImportErrorRow]


class KpiSummary(BaseModel):
    total: int
    next_employee_no: str
    max_employee_no: str | None
    created_this_month: int


class TrendBucket(BaseModel):
    month: str  # 'YYYY-MM'
    count: int


class SourceBucket(BaseModel):
    source: str
    count: int


class HireYearBucket(BaseModel):
    year: str  # 'YYYY' or 'unknown'
    count: int


class EmployeeNumberReportResponse(BaseModel):
    kpi: KpiSummary
    monthly_trend: list[TrendBucket]
    source_distribution: list[SourceBucket]
    hire_year_distribution: list[HireYearBucket]