render

type Context struct {
	// Renderer holds the rendering functions.
	Renderer *Renderer

	// The args map contains predefined variables that are
	// substituted into the query. It may be empty or nil.
	Args map[string]string

	// Fragments is the set of fragments that are rendered into
	// a SQL query. It may not be initialized until late in
	// the day.
	Fragments *Fragments

	// Dialect is the driver dialect.
	Dialect dialect.Dialect
}

type Fragments struct {
	Distinct string
	Columns  string
	From     string
	Where    string
	GroupBy  string
	Having   string
	OrderBy  string
	Range    string
	// PreExecStmts are statements that are executed before the query.
	// These can be used for edge-case behavior, such as setting up
	// variables in the session.
	//
	// See also: Fragments.PostExecStmts.
	PreExecStmts []string

	// PostExecStmts are statements that are executed after the query.
	//
	// See also: Fragments.PreExecStmts.
	PostExecStmts []string
}

type Renderer struct {
	// FromTable renders a FROM table fragment.
	FromTable func(rc *Context, tblSel *ast.TblSelectorNode) (string, error)

	// SelectCols renders a column names/expression fragment.
	// It shouldn't render the actual SELECT keyword. Example return value:
	//
	//   "first_name" AS "given_name", "last name" AS "family_name"
	SelectCols func(rc *Context, cols []ast.ResultColumn) (string, error)

	// Range renders a row range fragment.
	Range func(rc *Context, rr *ast.RowRangeNode) (string, error)

	// OrderBy renders the ORDER BY fragment.
	OrderBy func(rc *Context, ob *ast.OrderByNode) (string, error)

	// GroupBy renders the GROUP BY fragment.
	GroupBy func(rc *Context, gb *ast.GroupByNode) (string, error)

	// Having renders the HAVING fragment.
	Having func(rc *Context, having *ast.HavingNode) (string, error)

	// Join renders a join fragment.
	Join func(rc *Context, leftTbl *ast.TblSelectorNode, joins []*ast.JoinNode) (string, error)

	// Function renders a function fragment.
	Function func(rc *Context, fn *ast.FuncNode) (string, error)

	// FunctionNames is a map of SLQ function name to SQL function name.
	// It can be used by the Renderer.Function impl. Note that FunctionOverrides
	// has precedence over FunctionNames.
	FunctionNames map[string]string

	// FunctionOverrides is a map of SLQ function name to a custom
	// function to render that function. It can be used by the Renderer.Function
	// imp. FunctionOverrides has precedence over FunctionNames.
	FunctionOverrides map[string]func(rc *Context, fn *ast.FuncNode) (string, error)

	// Literal renders a literal fragment.
	Literal func(rc *Context, lit *ast.LiteralNode) (string, error)

	// Where renders a WHERE fragment.
	Where func(rc *Context, where *ast.WhereNode) (string, error)

	// Expr renders an expression fragment.
	Expr func(rc *Context, expr *ast.ExprNode) (string, error)

	// Operator renders an operator fragment.
	Operator func(rc *Context, op *ast.OperatorNode) (string, error)

	// Distinct renders the DISTINCT fragment. Returns an
	// empty string if n is nil.
	Distinct func(rc *Context, n *ast.UniqueNode) (string, error)

	// Render renders f into a SQL query.
	Render func(rc *Context, f *Fragments) (string, error)

	// PreRender is a set of hooks that are called before Render. It is a final
	// opportunity to customize f before rendering. It is nil by default.
	PreRender []func(rc *Context, f *Fragments) error
}