trail-sense-database-persistence

Trail-Sense Database Persistence

Add Room database persistence for a domain model following Trail-Sense patterns.

File Locations

app/src/main/java/com/kylecorry/trail_sense/tools/{toolName}/
├── domain/
│   └── {Model}.kt                    # Domain model (if not already exists)
└── infrastructure/persistence/
    ├── {Model}Entity.kt              # Room entity
    ├── {Model}Dao.kt                 # DAO interface
    └── {Model}Repo.kt                # Repository

Also update:

• app/src/main/java/com/kylecorry/trail_sense/main/persistence/AppDatabase.kt
• app/src/main/java/com/kylecorry/trail_sense/main/persistence/Converters.kt (if new types needed)
• {ToolName}ToolRegistration.kt - register repo singleton

Workflow

1. Create Entity with mapping functions
2. Create DAO interface
3. Add DAO to AppDatabase and create migration
4. Create Repository
5. Register repo singleton in ToolRegistration

1. Entity

package com.kylecorry.trail_sense.tools.{toolname}.infrastructure.persistence

import androidx.room.ColumnInfo
import androidx.room.Entity
import androidx.room.Index
import androidx.room.PrimaryKey
import com.kylecorry.trail_sense.tools.{toolname}.domain.{Model}

@Entity(
    tableName = "{table_name}",  // plural, lowercase, snake_case
    indices = [
        // Add indices for foreign keys and frequently queried columns
        // Index(value = ["parent_id"]),
        // Index(value = ["time"])
    ]
)
data class {Model}Entity(
    @ColumnInfo(name = "column_name") val property: Type,
    // ... other properties
) {
    @PrimaryKey(autoGenerate = true)
    @ColumnInfo(name = "_id")
    var id: Long = 0

    fun to{Model}(): {Model} {
        return {Model}(
            id = id,
            // Map entity properties to domain model
        )
    }

    companion object {
        fun from(model: {Model}): {Model}Entity {
            return {Model}Entity(
                // Map domain model properties to entity
            ).also {
                it.id = model.id
            }
        }
    }
}

Index Guidelines

Add indices for:

• Foreign key columns (e.g., parent_id, group_id)
• Time-based columns if queried by time range
• Columns used in WHERE clauses frequently
• Composite indices for multi-column filters: Index(value = ["col1", "col2"])

Type Mapping

• Instant -> stored as Long (epoch millis), converter exists
• Duration -> stored as Long (millis), converter exists
• Coordinate -> split into latitude: Double, longitude: Double
• Distance -> store as Float in meters
• Enums with id property -> use existing converters or add to Converters.kt
• AppColor -> converter exists
• Lists/collections -> join to comma-separated string, parse in mapping

2. DAO

package com.kylecorry.trail_sense.tools.{toolname}.infrastructure.persistence

import androidx.room.Dao
import androidx.room.Delete
import androidx.room.Query
import androidx.room.Upsert
import kotlinx.coroutines.flow.Flow

@Dao
interface {Model}Dao {
    @Query("SELECT * FROM {table_name}")
    fun getAll(): Flow<List<{Model}Entity>>

    @Query("SELECT * FROM {table_name}")
    suspend fun getAllSync(): List<{Model}Entity>

    @Query("SELECT * FROM {table_name} WHERE _id = :id LIMIT 1")
    suspend fun get(id: Long): {Model}Entity?

    @Upsert
    suspend fun upsert(entity: {Model}Entity): Long

    @Delete
    suspend fun delete(entity: {Model}Entity)
}

Optional DAO Methods

// Filter by parent/group
@Query("SELECT * FROM {table_name} WHERE parent_id IS :parentId")
suspend fun getAllInGroup(parentId: Long?): List<{Model}Entity>

// Time-based cleanup
@Query("DELETE FROM {table_name} WHERE time < :minEpochMillis")
suspend fun deleteOlderThan(minEpochMillis: Long)

// Get latest
@Query("SELECT * FROM {table_name} ORDER BY _id DESC LIMIT 1")
suspend fun getLast(): {Model}Entity?

3. AppDatabase Updates

Add Entity to Database

In AppDatabase.kt, add entity to @Database annotation:

@Database(
    entities = [..., {Model}Entity::class],
    version = {NEXT_VERSION},  // Increment from current
    exportSchema = false
)

Add DAO Accessor

abstract fun {model}Dao(): {Model}Dao

Add Migration

Inside buildDatabase(), add migration before the return Room.databaseBuilder:

val MIGRATION_{PREV}_{NEXT} = object : Migration({PREV}, {NEXT}) {
    override fun migrate(db: SupportSQLiteDatabase) {
        db.execSQL("""
            CREATE TABLE IF NOT EXISTS `{table_name}` (
                `_id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
                `column_name` TEXT NOT NULL,
                `nullable_column` TEXT DEFAULT NULL
                -- Match column types: TEXT, INTEGER, REAL
                -- NOT NULL for non-nullable, DEFAULT NULL for nullable
            )
        """.trimIndent())

        // Add indices if defined in entity
        // db.execSQL("CREATE INDEX IF NOT EXISTS index_{table_name}_{column} ON {table_name}({column})")
    }
}

Register Migration

Add to .addMigrations():

.addMigrations(
    ...,
    MIGRATION_{PREV}_{NEXT}
)

4. Repository

package com.kylecorry.trail_sense.tools.{toolname}.infrastructure.persistence

import android.annotation.SuppressLint
import android.content.Context
import com.kylecorry.luna.coroutines.onIO
import com.kylecorry.trail_sense.main.persistence.AppDatabase
import com.kylecorry.trail_sense.tools.{toolname}.domain.{Model}
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.flowOn
import kotlinx.coroutines.flow.map

class {Model}Repo private constructor(context: Context) {

    private val dao = AppDatabase.getInstance(context).{model}Dao()

    fun getAll(): Flow<List<{Model}>> = dao.getAll()
        .map { it.map { entity -> entity.to{Model}() } }
        .flowOn(Dispatchers.IO)

    suspend fun getAllSync(): List<{Model}> = onIO {
        dao.getAllSync().map { it.to{Model}() }
    }

    suspend fun get(id: Long): {Model}? = onIO {
        dao.get(id)?.to{Model}()
    }

    suspend fun add(model: {Model}): Long = onIO {
        dao.upsert({Model}Entity.from(model))
    }

    suspend fun delete(model: {Model}) = onIO {
        dao.delete({Model}Entity.from(model))
    }

    companion object {
        @SuppressLint("StaticFieldLeak")
        private var instance: {Model}Repo? = null

        @Synchronized
        fun getInstance(context: Context): {Model}Repo {
            if (instance == null) {
                instance = {Model}Repo(context.applicationContext)
            }
            return instance!!
        }
    }
}

5. Register Singleton in ToolRegistration

In {ToolName}ToolRegistration.kt, add the repo to singletons:

object {ToolName}ToolRegistration : ToolRegistration {
    override fun getTool(context: Context): Tool {
        return Tool(
            // ... other properties
            singletons = listOf(
                {Model}Repo::getInstance
            ),
            // ...
        )
    }
}

SQL Type Reference

Kotlin Type	SQLite Type	Notes
Long, Int	INTEGER
Double, Float	REAL
String	TEXT
Boolean	INTEGER	0/1
Instant	INTEGER	epoch millis
Enums	INTEGER	via id property
Nullable	Add DEFAULT NULL