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actions.go
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actions.go
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package kyoto
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"html/template"
"log"
"net/http"
"strings"
)
// ****************
// Action configuration
// ****************
// ActionConfiguration holds a global actions configuration.
type ActionConfiguration struct {
Path string // Configure a path prefix for action calls
}
// ActionConf is a global configuration that will be used during actions handling.
// See ActionConfiguration for more details.
var ActionConf = ActionConfiguration{
Path: "/internal/actions/",
}
// ****************
// Action parameters representation
// ****************
// ActionParameters is a Go representation of an action request.
type ActionParameters struct {
Component string
Action string
State string
Args []any
processed bool
}
// Parse extracts action data from a provided request.
func (p *ActionParameters) Parse(r *http.Request) error {
// Validate request format
if r.FormValue("State") == "" {
return errors.New("state is empty")
}
if r.FormValue("Args") == "" {
return errors.New("args is empty")
}
// Split path into tokens
tokens := strings.Split(r.URL.Path, "/")
// Extract component state as a raw json string (will be decoded with ActionPreload)
p.State = r.FormValue("State")
// Extract component arguments
err := json.Unmarshal([]byte(r.FormValue("Args")), &p.Args)
if err != nil {
return errors.New("something wrong with arguments")
}
// Extract component & action names
p.Component = tokens[len(tokens)-2]
p.Action = tokens[len(tokens)-1]
// Return
return nil
}
// ****************
// Action methods
// ****************
// Action is a function that handles an action request.
// Returns an execution flag (true if action was executed).
// You can use a flag to prevent farther execution of a component.
//
// Example:
//
// func Foo(ctx *kyoto.Context) (state FooState) {
// // Handle action
// bar := kyoto.Action(ctx, "Bar", func(args ...any) {
// // Do something
// })
// // Prevent further execution
// if bar {
// return
// }
// // Default non-action behavior
// // ...
// }
//
func Action(c *Context, name string, action func(args ...any)) bool {
// This will allow to avoid recursive action call
// while attaching recursive component
if c.Action.processed {
return false
}
if c.Action.Action == name {
action(c.Action.Args...)
c.Action.processed = true
return true
}
return false
}
// ActionPreload unpacks a component state from an action request.
// Executing only in case of an action request.
//
// Example:
//
// func CompFoo(ctx *kyoto.Context) (state CompFooState) {
// // Preload state
// kyoto.ActionPreload(ctx, &state)
// // Handle actions
// ...
// }
func ActionPreload[T any](c *Context, state T) {
// Pass if not an action
if c.Action.Component == "" {
return
}
// Unmarshal state
UnmarshalState(c.Action.State, state)
}
// ActionFlush allows to push multiple component UI updates during single action call.
// Call it when you need to push an updated component markup to the client.
//
// Example:
//
// func CompFoo(ctx *kyoto.Context) (state CompFooState) {
// ...
// // Handle example action
// kyoto.Action(ctx, "Bar", func(args ...any) {
// // Do something with a state
// state.Content = "Bar"
// // Push updated UI to the client
// kyoto.ActionFlush(ctx, state)
// // Do something else with a state
// state.Content = "Baz"
// // Push updated UI to the client
// kyoto.ActionFlush(ctx, state)
// })
// ...
// }
func ActionFlush(c *Context, state any) {
// Initialize flusher
flusher := c.ResponseWriter.(http.Flusher)
// Clone prepared template
tmpl, _ := c.Template.Clone()
// Render template into buffer
buf := &bytes.Buffer{}
if err := tmpl.Execute(buf, state); err != nil {
panic(err)
}
// Write to stream
if _, err := fmt.Fprint(c.ResponseWriter, buf.String()); err != nil {
panic(err)
}
// Flush
flusher.Flush()
}
// ****************
// Action template functions
// ****************
func actionFuncState(state any) template.HTMLAttr {
return template.HTMLAttr(fmt.Sprintf(`state="%s"`, MarshalState(state)))
}
func actionFuncClient() template.HTML {
builder := strings.Builder{}
builder.WriteString(fmt.Sprintf("<script>const ssapath = \"%s\"</script>", ActionConf.Path))
builder.WriteString(ActionClient)
return template.HTML(builder.String())
}
// ****************
// Action handling
// ****************
// HandleAction registers a component action handler with a predefined pattern in the DefaultServeMux.
// It's a wrapper around http.HandlePage, but accepts a component instead of usual http.HandlerFunc.
//
// Example:
//
// kyoto.HandleAction(CompFoo) // Register a usual component
// kyoto.handleAction(CompBar("")) // Register a component which accepts arguments and returns wrapped function
func HandleAction[T any](component Component[T]) {
pattern := ActionConf.Path + ComponentName(component) + "/"
log.Printf("Registering '%s' component action handler under '%s'", ComponentName(component), pattern)
http.HandleFunc(pattern, HandlerAction(component))
}
// HandlerAction returns a http.HandlerFunc that handles an action request for a specified component.
// Pattern still must to correspond to the provided component.
// It's recommended to use HandleAction instead.
//
// Example:
//
// http.HandleFunc("/internal/actions/Foo/", kyoto.HandlerAction(Foo))
func HandlerAction[T any](component Component[T]) func(w http.ResponseWriter, r *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
// Set headers
w.Header().Set("Content-Type", "plain/html")
w.Header().Set("Transfer-Encoding", "chunked")
w.Header().Set("Cache-Control", "no-store")
// Extract action parameters
a := ActionParameters{}
if err := a.Parse(r); err != nil {
panic(err)
}
// Prepare context
ctx := &Context{
ResponseWriter: w,
Request: r,
Action: a,
}
// Prepare template
TemplateInline(ctx, fmt.Sprintf(`{{ template "%s" . }}`, a.Component))
// Trigger building
state := component(ctx)
// Trigger flush
ActionFlush(ctx, state)
}
}