main.gala

package main

import (
    . "github.com/martianoff/gala-tui"
    . "martianoff/gala/collection_immutable"
    . "martianoff/gala/std"
)

// ============================================================================
// custom_widget — author your own widget with its own event vocabulary.
//
//     gala build ./examples/custom_widget
//     ./gala_tui.exe                        # binary takes the module name
//
// We define a `RatingView` widget — a horizontal row of star symbols —
// that exposes a single `OnSet(score)` event. Clicking a star sets the
// rating. Keyboard arrows + Enter also work. Both inputs share the same
// model field, so the rating reflects whichever path the user took.
//
// The takeaway: a user-authored widget defines its own constructor that
// takes typed callbacks and attaches them to interactive sub-regions
// with the fluent `.OnClick(msg)` method. Call sites read the widget
// like a built-in.
//
// All Msg cases use the `Cw` prefix because dot-importing gala-tui pulls
// in sealed-type case constructors (`NoOp`, `Quit`, `Up`, `Down`, …)
// that would otherwise shadow generic names.
// ============================================================================

struct Model(Score int, Max int)

sealed type Msg {
    case CwSet(Score int)        // rating changed (set absolute score)
    case CwLeft()                 // arrow-left  → bump score down
    case CwRight()                // arrow-right → bump score up
    case CwQuit()
    case CwNoOp()
}

// ----- The user-authored widget --------------------------------------------

// RatingView renders `r.Score` filled stars followed by `r.Max - r.Score`
// empty stars. Each star fires `OnSet(starIndex + 1)` on click — i.e.,
// clicking the third star sets Score to 3.
//
// The constructor's `OnSet` parameter is the entire event contract.
// Each cell uses the fluent `.OnClick(msg)` method to attach its click
// payload — no wrapper widgets visible in the call shape.
func RatingView[T any](
    r Model,
    OnSet func(int) T,
) Widget {
    val cells = ArrayTabulate(r.Max, (i) => {
        val star = i + 1                                      // 1-based score
        val glyph = if (star <= r.Score) "★" else "☆"
        val style = if (star <= r.Score)
            DefaultStyle().WithBold().WithFg(BrightYellow())
        else
            DefaultStyle().WithDim()
        val cell = TextStyled(" " + glyph + " ", style).OnClick(OnSet(star))
        return Fixed(3, cell)
    })
    return Row(cells)
}

// ----- Plumbing ------------------------------------------------------------

func update(m Model, msg Msg) Tuple[Model, Cmd[Msg]] = msg match {
    case CwQuit()   => (m, QuitCmd[Msg]())
    case CwNoOp()   => (m, NoCmd[Msg]())
    case CwSet(s)   => (m.Copy(Score = clamp(s, 0, m.Max)), NoCmd[Msg]())
    case CwLeft()   => (m.Copy(Score = clamp(m.Score - 1, 0, m.Max)), NoCmd[Msg]())
    case CwRight()  => (m.Copy(Score = clamp(m.Score + 1, 0, m.Max)), NoCmd[Msg]())
}

func clamp(v int, lo int, hi int) int {
    if v < lo { return lo }
    if v > hi { return hi }
    return v
}

func view(m Model) Widget {
    val title = TextStyled(" Rate this thing  (←/→ to adjust, or click a star) ",
        DefaultStyle().WithBold())
    // Use the user-authored widget exactly like a built-in:
    val rating = RatingView[Msg](m, (s) => CwSet(Score = s))
    val footer = TextStyled(s"  Score: ${m.Score} / ${m.Max}    (q to quit)",
        DefaultStyle().WithDim())
    return Column(ArrayOf[LayoutChild](
        Fixed(1, title),
        Fixed(1, Text("")),
        Fixed(1, rating),
        Fixed(1, Text("")),
        Fixed(1, footer),
    ))
}

func keyToMsg(ev KeyEvent) Msg {
    if KeyMatchesAny(ev, "ctrl+c", "q") { return CwQuit() }
    return ev.Key match {
        case ArrowLeft()  => CwLeft()
        case ArrowRight() => CwRight()
        case _            => CwNoOp()
    }
}

// inputToMsg only sees non-click events — the framework dispatches
// left-clicks against the registry before this function runs.
func inputToMsg(ev InputEvent) Msg = ev match {
    case KeyInput(k)   => keyToMsg(k)
    case MouseInput(_) => CwNoOp()
    case _             => CwNoOp()
}

func main() {
    val _ = RunSimpleWithMouse[Model, Msg](
        Model(Score = 3, Max = 5),
        update, view, inputToMsg,
        NoSubs[Msg](),
    )
}