boltdb example

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "github.com/boltdb/bolt"
    "log"
    "time"
)

// Config type
type Config struct {
    Height   float64   `json:"height"`
    Birthday time.Time `json:"birthday"`
}

// Entry type
type Entry struct {
    Calories int    `json:"calories"`
    Food     string `json:"food"`
}

func main() {
    db, err := setupDB()
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    conf := Config{Height: 186.0, Birthday: time.Now()}
    err = setConfig(db, conf)
    if err != nil {
        log.Fatal(err)
    }
    err = addWeight(db, "85.0", time.Now())
    if err != nil {
        log.Fatal(err)
    }
    err = addEntry(db, 100, "apple", time.Now())
    if err != nil {
        log.Fatal(err)
    }

    err = addEntry(db, 100, "orange", time.Now().AddDate(0, 0, -2))
    if err != nil {
        log.Fatal(err)
    }

    err = db.View(func(tx *bolt.Tx) error {
        conf := tx.Bucket([]byte("DB")).Get([]byte("CONFIG"))
        fmt.Printf("Config: %s\n", conf)
        return nil
    })
    if err != nil {
        log.Fatal(err)
    }

    err = db.View(func(tx *bolt.Tx) error {
        b := tx.Bucket([]byte("DB")).Bucket([]byte("WEIGHT"))
        b.ForEach(func(k, v []byte) error {
            fmt.Println(string(k), string(v))
            return nil
        })
        return nil
    })
    if err != nil {
        log.Fatal(err)
    }

    err = db.View(func(tx *bolt.Tx) error {
        c := tx.Bucket([]byte("DB")).Bucket([]byte("ENTRIES")).Cursor()
        min := []byte(time.Now().AddDate(0, 0, -7).Format(time.RFC3339))
        max := []byte(time.Now().AddDate(0, 0, 0).Format(time.RFC3339))
        for k, v := c.Seek(min); k != nil && bytes.Compare(k, max) <= 0; k, v = c.Next() {
            fmt.Println(string(k), string(v))
        }
        return nil
    })
    if err != nil {
        log.Fatal(err)
    }
}

func setupDB() (*bolt.DB, error) {
    db, err := bolt.Open("test.db", 0600, nil)
    if err != nil {
        return nil, fmt.Errorf("could not open db, %v", err)
    }
    err = db.Update(func(tx *bolt.Tx) error {
        root, err := tx.CreateBucketIfNotExists([]byte("DB"))
        if err != nil {
            return fmt.Errorf("could not create root bucket: %v", err)
        }
        _, err = root.CreateBucketIfNotExists([]byte("WEIGHT"))
        if err != nil {
            return fmt.Errorf("could not create weight bucket: %v", err)
        }
        _, err = root.CreateBucketIfNotExists([]byte("ENTRIES"))
        if err != nil {
            return fmt.Errorf("could not create days bucket: %v", err)
        }
        return nil
    })
    if err != nil {
        return nil, fmt.Errorf("could not set up buckets, %v", err)
    }
    fmt.Println("DB Setup Done")
    return db, nil
}

func setConfig(db *bolt.DB, config Config) error {
    confBytes, err := json.Marshal(config)
    if err != nil {
        return fmt.Errorf("could not marshal config json: %v", err)
    }
    err = db.Update(func(tx *bolt.Tx) error {
        err = tx.Bucket([]byte("DB")).Put([]byte("CONFIG"), confBytes)
        if err != nil {
            return fmt.Errorf("could not set config: %v", err)
        }
        return nil
    })
    fmt.Println("Set Config")
    return err
}

func addWeight(db *bolt.DB, weight string, date time.Time) error {
    err := db.Update(func(tx *bolt.Tx) error {
        err := tx.Bucket([]byte("DB")).Bucket([]byte("WEIGHT")).Put([]byte(date.Format(time.RFC3339)), []byte(weight))
        if err != nil {
            return fmt.Errorf("could not insert weight: %v", err)
        }
        return nil
    })
    fmt.Println("Added Weight")
    return err
}

func addEntry(db *bolt.DB, calories int, food string, date time.Time) error {
    entry := Entry{Calories: calories, Food: food}
    entryBytes, err := json.Marshal(entry)
    if err != nil {
        return fmt.Errorf("could not marshal entry json: %v", err)
    }
    err = db.Update(func(tx *bolt.Tx) error {
        err := tx.Bucket([]byte("DB")).Bucket([]byte("ENTRIES")).Put([]byte(date.Format(time.RFC3339)), entryBytes)
        if err != nil {
            return fmt.Errorf("could not insert entry: %v", err)
        }

        return nil
    })
    fmt.Println("Added Entry")
    return err
}

#go run main.go
DB Setup Done
Set Config
Added Weight
Added Entry
Added Entry
Config: {"height":186,"birthday":"2023-05-23T20:34:37.185488195+08:00"}
2023-05-23T20:34:37+08:00 85.0
2023-05-21T20:34:37+08:00 {"calories":100,"food":"orange"}
2023-05-23T20:34:37+08:00 {"calories":100,"food":"apple"}