refactor: remove deprecated course duration/lessons fields and simplify mappings

openspec/changes/refactor-dto-and-companion-value-wrapping/.openspec.yaml

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+schema: spec-driven
+created: 2026-08-19
+skip_specs: true

openspec/changes/refactor-dto-and-companion-value-wrapping/design.md

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+## Context
+
+See [proposal.md](proposal.md) for the motivation of this change.
+
+1. `CourseDto.fromJson` assigns both `totalContents` and `totalLessons` from `'contents_count'`. `totalDuration` is also a deprecated field.
+2. In `CoursesTable` (`packages/core/lib/data/db/tables/courses_table.dart`), both `totalDuration` and `totalLessons` exist as columns. Since the app has not been released yet, we can safely delete these columns from the database without a schema migration.
+3. In `CourseRepository` (`packages/courses/lib/repositories/course_repository.dart`), `_lessonDtoToCompanion` method uses verbose conditional expressions `val != null ? Value(val) : const Value.absent()` for over 30 nullable fields.
+
+## Goals / Non-Goals
+
+**Goals:**
+- Completely remove `totalDuration` and `totalLessons` from `CourseDto` and `CoursesTable`.
+- Update UI references in `course_card.dart` and `info_page.dart` to use `totalContents`.
+- Regenerate generated drift file `app_database.g.dart` to apply the database schema changes.
+- Refactor `_lessonDtoToCompanion` to use `Value.absentIfNull` for all nullable fields to simplify mapping logic.
+
+**Non-Goals:**
+- Database schema migration scripts (since this is pre-release code).
+
+## Decisions
+
+### 1. Completely remove `totalDuration` and `totalLessons` columns and fields
+We will:
+- Delete `totalDuration` and `totalLessons` columns from `CoursesTable` in `courses_table.dart`.
+- Delete `totalDuration` and `totalLessons` fields from `CourseDto` in `course_dto.dart`.
+- Transition all UI files (`course_card.dart` and `info_page.dart`) and repository mapping helpers to use `totalContents`.
+- Regenerate the database files using `dart run build_runner build --delete-conflicting-outputs` in the core package.
+
+### 2. Refactor `_lessonDtoToCompanion` to use `Value.absentIfNull`
+For all nullable fields mapped from `LessonDto` to `LessonsTableCompanion` in `packages/courses/lib/repositories/course_repository.dart`, we will replace `dto.field != null ? Value(dto.field) : const Value.absent()` with `Value.absentIfNull(dto.field)`.
+
+## Risks / Trade-offs
+
+- **Risk:** Build runner fails or other packages depend on the removed columns.
+  - **Mitigation:** Run `flutter analyze` on the entire monorepo after code generation to resolve any remaining references to `totalLessons` or `totalDuration`.
+

openspec/changes/refactor-dto-and-companion-value-wrapping/proposal.md

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+## Why
+
+1. `CourseDto.fromJson` contains a dead assignment where both `totalContents` and `totalLessons` are parsed from `json['contents_count']`. Because `totalLessons` is deprecated and redundant with `totalContents`, it should be completely removed, alongside the old deprecated `totalDuration` field.
+2. The app is not released yet, so we can clean up the database columns `totalDuration` and `totalLessons` in `CoursesTable` directly without needing schema migrations.
+3. `_lessonDtoToCompanion` in `CourseRepository` contains over 30 lines of verbose conditional checks for nullable fields (`dto.field != null ? Value(dto.field) : const Value.absent()`). These can be simplified using Drift's native `Value.absentIfNull` constructor to improve readability.
+
+## What Changes
+
+- Remove `totalDuration` and `totalLessons` fields completely from `CourseDto`.
+- Remove `totalDuration` and `totalLessons` columns from `CoursesTable` in `courses_table.dart`, and regenerate drift schema.
+- Update repository mapping functions (`rowToCourseDto` and `_courseDtoToCompanion`) to omit removed fields.
+- Refactor the 30+ field mappings in `_lessonDtoToCompanion` to use `Value.absentIfNull`.
+
+## Capabilities
+
+### New Capabilities
+<!-- None — this is a pure refactor change with no requirement/behavior changes -->
+
+### Modified Capabilities
+<!-- None — this is a pure refactor change with no requirement/behavior changes -->
+
+> **Note:** This is a pure refactor / code cleanup. No spec-level behaviour changes.
+> `skip_specs: true` has been set in `.openspec.yaml`.
+
+## Impact
+
+- **Files:** 
+  - `packages/core/lib/data/models/course_dto.dart`
+  - `packages/core/lib/data/db/tables/courses_table.dart`
+  - `packages/courses/lib/repositories/course_repository.dart`
+- **Scope:** Cleanups of JSON deserialization, database schema, and DB companion mapping.
+- **Risk:** Medium (requires regenerating code and checking all usages of these fields/columns).

openspec/changes/refactor-dto-and-companion-value-wrapping/tasks.md

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+## 1. DTO and Database Column Removal
+
+- [x] 1.1 Delete `totalDuration` and `totalLessons` fields from `CourseDto` (`packages/core/lib/data/models/course_dto.dart`)
+- [x] 1.2 Delete `totalDuration` and `totalLessons` columns from `CoursesTable` (`packages/core/lib/data/db/tables/courses_table.dart`)
+- [x] 1.3 Update repository mapping helpers (`rowToCourseDto` and `_courseDtoToCompanion` in `course_repository.dart`) to completely omit these removed columns and DTO fields
+- [x] 1.4 Run drift code generation (`dart run build_runner build --delete-conflicting-outputs` inside `packages/core`) to regenerate `app_database.g.dart`
+- [x] 1.5 Fix `totalLessons` usages and compiler errors in `packages/exams`
+- [x] 1.6 Fix `totalDuration` usages and dynamic list return type compiler error in `packages/profile`
+
+## 2. Refactor Companion Mappings
+
+- [x] 2.1 Refactor the 30+ nullable mapping fields in `_lessonDtoToCompanion` inside `packages/courses/lib/repositories/course_repository.dart` to use `Value.absentIfNull`
+
+## 3. Verification
+
+- [x] 3.1 Run static analysis across `packages/courses` and `packages/core` to ensure compilation is clean and all deprecated field usages are resolved
+- [x] 3.2 Run test suite in `packages/courses` to verify no regressions are introduced
+