import json
from typing import Annotated, Any, Literal

from pydantic import AwareDatetime, BaseModel, ConfigDict, Field, StringConstraints, field_validator, model_validator

RunStatus = Literal["running", "success", "warning", "failed"]
Name = Annotated[str, StringConstraints(strip_whitespace=True, min_length=1, max_length=200)]

MAX_MESSAGE_CHARS = 32_000
MAX_DETAILS_BYTES = 16_000


class Strict(BaseModel):
    # Reject unknown fields so a typo in a collector script fails loudly instead of being dropped.
    model_config = ConfigDict(extra="forbid")


class JobIn(Strict):
    external_id: Name = Field(description="The source system's own stable ID for the job")
    name: Name
    # Omit to leave the stored value untouched; send null to clear it.
    next_run_at: AwareDatetime | None = None


class RunIn(Strict):
    external_id: Name | None = Field(
        None, description="The source's ID for this run. Defaults to started_at, so a 'running' "
                          "report and its later completion report merge into one run.")
    status: RunStatus
    started_at: AwareDatetime
    # Omit for a finished run to use the time the report was received.
    finished_at: AwareDatetime | None = None
    message: str = ""
    size_bytes: int | None = Field(None, ge=0)
    details: dict[str, Any] = Field(default_factory=dict)

    @field_validator("message")
    @classmethod
    def truncate_message(cls, v: str) -> str:
        # Backup logs can be huge; keep the head, which is where the summary usually is.
        return v if len(v) <= MAX_MESSAGE_CHARS else v[:MAX_MESSAGE_CHARS] + "\n… [truncated]"

    @field_validator("details")
    @classmethod
    def limit_details(cls, v: dict[str, Any]) -> dict[str, Any]:
        if len(json.dumps(v)) > MAX_DETAILS_BYTES:
            raise ValueError(f"details must serialize to at most {MAX_DETAILS_BYTES} bytes")
        return v

    @model_validator(mode="after")
    def check_times(self) -> "RunIn":
        if self.status == "running" and self.finished_at is not None:
            raise ValueError("a running run cannot have finished_at")
        if self.finished_at is not None and self.finished_at < self.started_at:
            raise ValueError("finished_at is before started_at")
        return self


class IngestIn(Strict):
    tenant: Name = Field(description="Company name as shown on the dashboard")
    source_system: Annotated[str, StringConstraints(strip_whitespace=True, min_length=1, max_length=100)]
    job: JobIn
    run: RunIn | None = Field(None, description="Omit to only register/update the job (e.g. next_run_at)")