mirror of https://github.com/VinGarcia/ksql.git
67 lines
2.1 KiB
Go
67 lines
2.1 KiB
Go
package ksql
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import (
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"context"
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"database/sql/driver"
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"fmt"
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)
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// Here we keep all the registered modifier
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var modifiers = map[string]AttrModifier{
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"json": jsonModifier{},
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}
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// RegisterAttrModifier allow users to add custom modifiers on startup
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// it is recommended to do this inside an init() function.
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func RegisterAttrModifier(key string, modifier AttrModifier) {
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_, found := modifiers[key]
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if found {
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panic(fmt.Errorf("KSQL: cannot register modifier '%s' name is already in use", key))
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}
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modifiers[key] = modifier
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}
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// AttrModifier describes the two operations required to serialize and deserialize an object from the database.
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type AttrModifier interface {
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AttrScan(ctx context.Context, opInfo OpInfo, attrPtr interface{}, dbValue interface{}) error
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AttrValue(ctx context.Context, opInfo OpInfo, inputValue interface{}) (outputValue interface{}, _ error)
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}
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// OpInfo contains information that might be used by a modifier to determine how it should behave.
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type OpInfo struct {
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// A string version of the name of one of
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// the methods of the `ksql.Provider` interface, e.g. `Insert` or `Query`
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Method string
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// The string representing the current underlying database, e.g.:
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// "postgres", "sqlite3", "mysql" or "sqlserver".
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DriverName string
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}
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// attrModifier is the wrapper that allow us to intercept the Scan and Value processes
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// so we can run the modifiers instead of allowing the database driver to use
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// its default behavior.
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//
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// For that this struct implements both the `sql.Scanner` and `sql.Valuer` interfaces.
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type attrModifier struct {
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ctx context.Context
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// When Scanning this value should be a pointer to the attribute
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// and when "Valuing" it should just be the actual value
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attr interface{}
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modifierName string
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opInfo OpInfo
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}
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// Scan implements the sql.Scanner interface
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func (a attrModifier) Scan(dbValue interface{}) error {
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return modifiers[a.modifierName].AttrScan(a.ctx, a.opInfo, a.attr, dbValue)
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}
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// Value implements the sql.Valuer interface
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func (a attrModifier) Value() (driver.Value, error) {
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return modifiers[a.modifierName].AttrValue(a.ctx, a.opInfo, a.attr)
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}
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