"""
Core domain models for activity-core.

T01: EventEnvelope — standard envelope for all inbound and outbound events.
T02: ActivityDefinition — versioned definition of a trigger + context resolver + task templates.
"""

from __future__ import annotations

from typing import Annotated, Any, Literal, Union
from datetime import datetime
from uuid import UUID

from pydantic import BaseModel, Field


# ── T01: Event Envelope ────────────────────────────────────────────────────────

class EventEnvelope(BaseModel):
    """Standard internal event envelope. Every event, whether time-fired or
    broker-delivered, is normalised into this shape before processing."""

    event_id: str = Field(
        description="Stable unique ID. Used for deduplication: if an event with "
                    "this ID has already been processed, the router skips it."
    )
    type: str = Field(description="Dot-namespaced event type, e.g. 'user.created'.")
    source: str = Field(description="Originating service or component, e.g. 'user-service'.")
    occurred_at: datetime = Field(description="When the event occurred (UTC).")
    subject: str = Field(description="Primary resource affected, e.g. 'user/123'.")
    trace_id: str = Field(description="Distributed tracing correlation ID.")
    schema_version: str = Field(
        default="1.0",
        description="Schema version string for forward-compatibility.",
    )
    payload: dict[str, Any] = Field(
        default_factory=dict,
        description="Event-specific data; structure varies by event type.",
    )


# ── T02: ActivityDefinition ────────────────────────────────────────────────────

class CronTriggerConfig(BaseModel):
    trigger_type: Literal["cron"] = "cron"
    cron_expression: str = Field(
        description="Standard 5-field cron expression, e.g. '0 9 * * 1-5'."
    )
    timezone: str = Field(
        default="UTC",
        description="IANA timezone name, e.g. 'Europe/Berlin'.",
    )
    jitter_seconds: int = Field(
        default=0,
        ge=0,
        description="Maximum random delay (seconds) added to each trigger to spread load.",
    )
    misfire_policy: Literal["skip", "catchup", "compress"] = Field(
        default="skip",
        description=(
            "skip: ignore any missed runs. "
            "catchup: replay missed runs up to a bounded limit. "
            "compress: run once covering the full missed window."
        ),
    )


class EventTriggerConfig(BaseModel):
    trigger_type: Literal["event"] = "event"
    event_type: str = Field(
        description="Matches EventEnvelope.type. The router fires this activity "
                    "when an event with this type is received."
    )
    filters: dict[str, Any] = Field(
        default_factory=dict,
        description="Optional predicate filters applied to EventEnvelope.payload "
                    "before routing. All filters must match for the activity to fire.",
    )


TriggerConfig = Annotated[
    Union[CronTriggerConfig, EventTriggerConfig],
    Field(discriminator="trigger_type"),
]


class ContextSource(BaseModel):
    """Describes one external data source that the workflow queries to build
    the context snapshot passed to evaluate_templates."""

    name: str = Field(
        description="Logical name; referenced as 'context.<name>' in task templates."
    )
    type: str = Field(
        description="Source adapter type: 'db_query' | 'http_get' | 'static'."
    )
    config: dict[str, Any] = Field(
        default_factory=dict,
        description="Source-specific configuration (SQL, URL, static value, etc.).",
    )


class TaskTemplate(BaseModel):
    """Template for one task instance produced by RunActivityWorkflow.

    evaluate_templates() expands each template against the context snapshot
    to produce a concrete TaskInstance."""

    task_type: str = Field(
        description="Maps to a registered TaskExecutorWorkflow type, e.g. 'send_email'."
    )
    condition: str | None = Field(
        default=None,
        description=(
            "Optional Python expression evaluated against the context snapshot. "
            "Task is skipped if the expression is falsy. "
            "Example: \"context['user']['is_active'] == True\""
        ),
    )
    params_template: dict[str, Any] = Field(
        default_factory=dict,
        description=(
            "Parameter template. String values starting with '{context.' are "
            "interpolated from the context snapshot at evaluation time."
        ),
    )


class ActivityDefinition(BaseModel):
    """Versioned definition of a single activity: its trigger, context resolution
    strategy, and the task templates it can spawn."""

    id: UUID = Field(
        description="Stable UUID. Used as the Temporal Schedule ID prefix "
                    "(f'activity-schedule-{id}') and as the workflow ID component."
    )
    name: str = Field(description="Human-readable name.")
    enabled: bool = Field(
        default=True,
        description="When False the corresponding Temporal Schedule is paused "
                    "and event routing is suppressed.",
    )
    trigger_config: TriggerConfig = Field(
        description="Cron or event trigger configuration."
    )
    context_sources: list[ContextSource] = Field(default_factory=list)
    task_templates: list[TaskTemplate] = Field(default_factory=list)
    dedupe_key_strategy: Literal["skip", "catchup", "compress"] = Field(
        default="skip",
        description="How to handle duplicate or missed trigger events. "
                    "Should match CronTriggerConfig.misfire_policy for cron activities.",
    )
    version: int = Field(
        default=1,
        ge=1,
        description="Incremented on breaking schema changes. Stored in activity_runs "
                    "for audit purposes.",
    )