"""Build the Learning Engine's authoritative, server-side planning context."""

from __future__ import annotations

from dataclasses import dataclass
from datetime import date, datetime, timedelta, timezone
from typing import Any

from sqlalchemy import select
from sqlalchemy.orm import Session

from app.models.learn_anything_roadmap import LearnAnythingRoadmap
from app.models.learning_state import (
    Chapter,
    DailyPlan,
    DailyTask,
    LearningEvent,
    LessonProgress,
    RepairItem,
    RevisionItem,
    StudentProfileState,
    StudyFollowUp,
    StudyPlan,
    Subject,
    TopicMastery,
)
from app.services.content_manifest import ContentManifest, load_content_manifest


def aware(value: datetime | None) -> datetime | None:
    if value is None:
        return None
    return value if value.tzinfo is not None else value.replace(tzinfo=timezone.utc)


@dataclass(frozen=True, slots=True)
class ProfileContext:
    class_level: str
    board: str
    exam_date: date | None
    goal: str
    daily_minutes: int
    preferred_time: str | None
    preferences: dict[str, Any]


@dataclass(frozen=True, slots=True)
class SubjectContext:
    id: str
    name: str
    priority: int


@dataclass(frozen=True, slots=True)
class ChapterContext:
    id: str
    subject_id: str
    catalog_id: str
    title: str
    order_index: int
    importance: float
    status: str
    curated: bool


@dataclass(frozen=True, slots=True)
class LessonContext:
    id: str
    chapter_id: str
    mission_id: str
    status: str
    progress_percent: int
    current_step: int
    last_seen_at: datetime


@dataclass(frozen=True, slots=True)
class MasteryContext:
    topic_key: str
    topic_label: str
    subject_id: str | None
    chapter_id: str | None
    score: float
    confidence: float
    attempts_count: int
    last_result: str | None
    next_review_at: datetime | None
    evidence: dict[str, Any]


@dataclass(frozen=True, slots=True)
class RepairContext:
    id: str
    subject_id: str | None
    chapter_id: str | None
    concept_key: str
    concept_label: str
    mission_id: str | None
    error_category: str
    diagnosis: str
    priority: float
    estimated_minutes: int
    failed_attempts: int
    created_at: datetime


@dataclass(frozen=True, slots=True)
class RevisionContext:
    id: str
    subject_id: str | None
    chapter_id: str | None
    mission_id: str | None
    topic_key: str | None
    title: str
    source_kind: str
    source_ref: str | None
    status: str
    due_at: datetime | None
    metadata: dict[str, Any]
    created_at: datetime


@dataclass(frozen=True, slots=True)
class ExistingTaskContext:
    id: str
    daily_plan_id: str | None
    subject_id: str | None
    chapter_id: str | None
    task_type: str
    title: str
    scheduled_for: datetime
    duration_minutes: int
    priority: float
    href: str | None
    mission_id: str | None
    metadata: dict[str, Any]


@dataclass(frozen=True, slots=True)
class RoadmapContext:
    row_id: str
    roadmap_id: str
    topic: str
    module_title: str | None
    task_key: str
    task_title: str
    estimated_minutes: int
    updated_at: datetime


@dataclass(frozen=True, slots=True)
class FollowUpContext:
    id: str
    chat_session_id: str
    kind: str
    title: str
    subject: str | None
    chapter: str | None
    topic: str | None
    due_at: datetime | None
    estimated_minutes: int
    source_ref: str | None
    target_data: dict[str, Any]


@dataclass(frozen=True, slots=True)
class PlanHistoryContext:
    date: date
    generation: int
    planned_minutes: int
    completed_minutes: int
    subject_minutes: tuple[tuple[str, int], ...]


@dataclass(frozen=True, slots=True)
class LearningContext:
    user_id: str
    now: datetime
    today: date
    profile: ProfileContext
    study_plan_id: str
    subjects: tuple[SubjectContext, ...]
    chapters: tuple[ChapterContext, ...]
    lessons: tuple[LessonContext, ...]
    mastery: tuple[MasteryContext, ...]
    repairs: tuple[RepairContext, ...]
    revisions: tuple[RevisionContext, ...]
    unfinished_tasks: tuple[ExistingTaskContext, ...]
    roadmaps: tuple[RoadmapContext, ...]
    followups: tuple[FollowUpContext, ...]
    recent_plan_history: tuple[PlanHistoryContext, ...]
    recent_event_types: tuple[str, ...]
    content: ContentManifest

    @property
    def days_to_exam(self) -> int | None:
        return (self.profile.exam_date - self.today).days if self.profile.exam_date else None


def _roadmap_context(row: LearnAnythingRoadmap) -> RoadmapContext | None:
    data = row.data if isinstance(row.data, dict) else {}
    modules = data.get("weeklyModules")
    statuses = data.get("topicStatus")
    if not isinstance(modules, list):
        return None
    statuses = statuses if isinstance(statuses, dict) else {}
    for module_index, module in enumerate(modules):
        if not isinstance(module, dict):
            continue
        tasks = module.get("tasks")
        if not isinstance(tasks, list):
            continue
        week = module.get("week", module_index + 1)
        for task_index, raw_title in enumerate(tasks):
            title = str(raw_title).strip()
            if not title:
                continue
            key = f"Week {week}::{task_index}"
            if statuses.get(key) in {"covered", "mastered"}:
                continue
            today_lesson = data.get("todayLesson")
            minutes = (
                int(today_lesson.get("minutes") or 15)
                if isinstance(today_lesson, dict)
                else 15
            )
            return RoadmapContext(
                row_id=row.id,
                roadmap_id=row.roadmap_id,
                topic=str(data.get("topic") or "Your course"),
                module_title=str(module.get("title") or "") or None,
                task_key=key,
                task_title=title,
                estimated_minutes=max(5, min(60, minutes)),
                updated_at=aware(row.updated_at) or datetime.now(timezone.utc),
            )
    return None


def load_learning_context(
    db: Session,
    *,
    user_id: str,
    now: datetime | None = None,
) -> LearningContext | None:
    current = aware(now) or datetime.now(timezone.utc)
    profile_row = db.scalar(
        select(StudentProfileState).where(StudentProfileState.user_id == user_id)
    )
    plan_row = db.scalar(
        select(StudyPlan)
        .where(StudyPlan.user_id == user_id, StudyPlan.status == "active")
        .order_by(StudyPlan.created_at.desc())
    )
    if profile_row is None or plan_row is None:
        return None

    subject_rows = list(
        db.scalars(
            select(Subject)
            .where(Subject.user_id == user_id, Subject.status == "active")
            .order_by(Subject.priority, Subject.name)
        )
    )
    chapter_rows = list(db.scalars(select(Chapter).where(Chapter.user_id == user_id)))
    lesson_rows = list(db.scalars(select(LessonProgress).where(LessonProgress.user_id == user_id)))
    mastery_rows = list(db.scalars(select(TopicMastery).where(TopicMastery.user_id == user_id)))
    repair_rows = list(
        db.scalars(
            select(RepairItem)
            .where(RepairItem.user_id == user_id, RepairItem.status.in_(("open", "escalated")))
            .order_by(RepairItem.priority.desc(), RepairItem.created_at)
        )
    )
    revision_rows = list(
        db.scalars(
            select(RevisionItem)
            .where(RevisionItem.user_id == user_id, RevisionItem.status.in_(("pending", "due")))
            .order_by(RevisionItem.due_at, RevisionItem.created_at)
        )
    )
    task_rows = list(
        db.scalars(
            select(DailyTask)
            .where(
                DailyTask.user_id == user_id,
                DailyTask.study_plan_id == plan_row.id,
                DailyTask.daily_plan_id.is_(None),
                DailyTask.status == "pending",
            )
            .order_by(DailyTask.scheduled_for, DailyTask.priority.desc())
        )
    )
    roadmap_rows = list(
        db.scalars(
            select(LearnAnythingRoadmap)
            .where(LearnAnythingRoadmap.user_id == user_id)
            .order_by(LearnAnythingRoadmap.updated_at.desc())
        )
    )
    followup_rows = list(
        db.scalars(
            select(StudyFollowUp)
            .where(StudyFollowUp.user_id == user_id, StudyFollowUp.status == "open")
            .order_by(StudyFollowUp.due_at, StudyFollowUp.created_at)
        )
    )
    history_rows = list(
        db.scalars(
            select(DailyPlan)
            .where(
                DailyPlan.user_id == user_id,
                DailyPlan.plan_date < current.date(),
                DailyPlan.plan_date >= current.date() - timedelta(days=7),
            )
            .order_by(DailyPlan.plan_date.desc())
        )
    )
    recent_events = list(
        db.scalars(
            select(LearningEvent)
            .where(
                LearningEvent.user_id == user_id,
                LearningEvent.occurred_at >= current - timedelta(days=14),
            )
            .order_by(LearningEvent.occurred_at.desc())
            .limit(100)
        )
    )

    history: list[PlanHistoryContext] = []
    for row in history_rows:
        subject_minutes: dict[str, int] = {}
        history_tasks = db.scalars(
            select(DailyTask).where(DailyTask.daily_plan_id == row.id)
        )
        for task in history_tasks:
            if task.subject_id:
                subject_minutes[task.subject_id] = subject_minutes.get(task.subject_id, 0) + task.duration_minutes
        history.append(
            PlanHistoryContext(
                date=row.plan_date,
                generation=row.generation,
                planned_minutes=row.planned_minutes,
                completed_minutes=row.completed_minutes,
                subject_minutes=tuple(sorted(subject_minutes.items())),
            )
        )

    roadmaps = tuple(item for row in roadmap_rows if (item := _roadmap_context(row)) is not None)
    return LearningContext(
        user_id=user_id,
        now=current,
        today=current.date(),
        profile=ProfileContext(
            class_level=profile_row.class_level,
            board=profile_row.board,
            exam_date=profile_row.exam_date,
            goal=profile_row.goal,
            daily_minutes=max(15, profile_row.daily_minutes),
            preferred_time=profile_row.preferred_time,
            preferences=dict(profile_row.preferences or {}),
        ),
        study_plan_id=plan_row.id,
        subjects=tuple(SubjectContext(row.id, row.name, row.priority) for row in subject_rows),
        chapters=tuple(
            ChapterContext(
                row.id,
                row.subject_id,
                row.catalog_id,
                row.title,
                row.order_index,
                row.importance,
                row.status,
                row.curated,
            )
            for row in chapter_rows
        ),
        lessons=tuple(
            LessonContext(
                row.id,
                row.chapter_id,
                row.mission_id,
                row.status,
                row.progress_percent,
                row.current_step,
                aware(row.last_seen_at) or current,
            )
            for row in lesson_rows
        ),
        mastery=tuple(
            MasteryContext(
                row.topic_key,
                row.topic_label,
                row.subject_id,
                row.chapter_id,
                row.score,
                row.confidence,
                row.attempts_count,
                row.last_result,
                aware(row.next_review_at),
                dict(row.evidence or {}),
            )
            for row in mastery_rows
        ),
        repairs=tuple(
            RepairContext(
                row.id,
                row.subject_id,
                row.chapter_id,
                row.concept_key,
                row.concept_label,
                row.mission_id,
                row.error_category,
                row.diagnosis,
                row.priority,
                row.estimated_minutes,
                row.failed_attempts,
                aware(row.created_at) or current,
            )
            for row in repair_rows
        ),
        revisions=tuple(
            RevisionContext(
                row.id,
                row.subject_id,
                row.chapter_id,
                row.mission_id,
                row.topic_key,
                row.title,
                row.source_kind,
                row.source_ref,
                row.status,
                aware(row.due_at),
                dict(row.item_data or {}),
                aware(row.created_at) or current,
            )
            for row in revision_rows
        ),
        unfinished_tasks=tuple(
            ExistingTaskContext(
                row.id,
                row.daily_plan_id,
                row.subject_id,
                row.chapter_id,
                row.task_type,
                row.title,
                aware(row.scheduled_for) or current,
                row.duration_minutes,
                row.priority,
                row.href,
                row.mission_id,
                dict(row.task_metadata or {}),
            )
            for row in task_rows
        ),
        roadmaps=roadmaps,
        followups=tuple(
            FollowUpContext(
                row.id,
                row.chat_session_id,
                row.kind,
                row.title,
                row.subject,
                row.chapter,
                row.topic,
                aware(row.due_at),
                row.estimated_minutes,
                row.source_ref,
                dict(row.target_data or {}),
            )
            for row in followup_rows
        ),
        recent_plan_history=tuple(history),
        recent_event_types=tuple(row.event_type for row in recent_events),
        content=load_content_manifest(),
    )