from django.core.exceptions import ValidationError
from django.conf import settings
from django.db import models
from django.db.models import Q

from apps.logs.services import build_workspace_log_metadata
from apps.logs.services.constants import SECTION_TIME_ENTRIES
from core.models.base import BaseModel
from apps.workspaces.models import Workspace
from apps.projects.models import Project
from apps.tags.models import Tag


User = settings.AUTH_USER_MODEL


class TimeEntry(BaseModel):
    workspace = models.ForeignKey(
        Workspace,
        on_delete=models.CASCADE,
        related_name="time_entries",
    )
    user = models.ForeignKey(
        User,
        on_delete=models.CASCADE,
        related_name="time_entries",
    )
    project = models.ForeignKey(
        Project,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="time_entries",
    )
    description = models.TextField(blank=True)
    start_time = models.DateTimeField()
    end_time = models.DateTimeField(null=True, blank=True)
    duration = models.DurationField(null=True, blank=True)
    tags = models.ManyToManyField(
        Tag,
        blank=True,
        related_name="time_entries",
    )
    is_billable = models.BooleanField(default=False)
    hourly_rate = models.DecimalField(
        max_digits=10,
        decimal_places=2,
        null=True,
        blank=True,
    )
    currency = models.CharField(
        max_length=3,
        default="USD",
    )

    class Meta:
        db_table = "time_entry"
        ordering = ("-updated_at", "-created_at")
        indexes = [
            models.Index(fields=["workspace"], name="time_entry_workspace_idx"),
            models.Index(fields=["user"], name="time_entry_user_idx"),
            models.Index(fields=["project"], name="time_entry_project_idx"),
            models.Index(fields=["start_time"], name="time_entry_start_idx"),
            models.Index(fields=["workspace", "start_time"], name="time_entry_workspace_start_idx"),
        ]
        constraints = [
            models.UniqueConstraint(
                fields=["workspace", "user"],
                condition=Q(end_time__isnull=True, is_deleted=False),
                name="unique_running_timer_per_user",
            )
        ]

    def __str__(self):
        return f"{self.user} - {self.start_time}"

    def get_additional_data(self):
        target_label = self.description.strip() if self.description else f"Time entry {self.start_time.isoformat()}"
        return build_workspace_log_metadata(
            section=SECTION_TIME_ENTRIES,
            workspace_id=self.workspace_id,
            target_id=self.id,
            target_label=target_label,
            extra={"entry_user_id": str(self.user_id)},
        )

    def clean(self):
        if self.project and self.project.workspace_id != self.workspace_id:
            raise ValidationError("Project must belong to the same workspace.")

        for tag in self.tags.all():
            if tag.workspace_id != self.workspace_id:
                raise ValidationError("Tags must belong to the same workspace.")