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// SPDX-FileCopyrightText: 2025 Shota FUJI <pockawoooh@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-only

//go:build js && wasm

package main

import (
	"context"
	"log/slog"
	"syscall/js"
)

type BrowserConsoleLogHandler struct {
	attrs  []slog.Attr
	group  string
	parent *BrowserConsoleLogHandler
}

func NewBrowserConsoleLogHandler() *BrowserConsoleLogHandler {
	return &BrowserConsoleLogHandler{
		attrs:  nil,
		group:  "",
		parent: nil,
	}
}

func (*BrowserConsoleLogHandler) Enabled(_ context.Context, _ slog.Level) bool {
	return true
}

func newObject() js.Value {
	obj := js.Global().Get("Object").Call("create", js.Null())
	return obj
}

func safeJsValueOf(x slog.Value) js.Value {
	switch x.Kind() {
	case slog.KindBool:
		return js.ValueOf(x.Bool())
	case slog.KindInt64:
		return js.ValueOf(x.Int64())
	case slog.KindUint64:
		return js.ValueOf(x.Uint64())
	case slog.KindFloat64:
		return js.ValueOf(x.Float64())
	case slog.KindGroup:
		group := newObject()
		for _, g := range x.Group() {
			group.Set(g.Key, safeJsValueOf(g.Value))
		}
		return group
	default:
		return js.ValueOf(x.String())
	}
}

func (h *BrowserConsoleLogHandler) getAttrsObject() (js.Value, js.Value) {
	var obj js.Value
	var root js.Value

	if h.parent == nil {
		root = newObject()

		obj = root
		if h.group != "" {
			child := newObject()
			root.Set(h.group, child)
			obj = child
		}

	} else {
		var parent js.Value
		parent, root = h.parent.getAttrsObject()

		obj = parent
		if h.group != "" {
			child := newObject()
			parent.Set(h.group, child)
			obj = child
		}
	}

	if len(h.attrs) == 0 {
		return obj, root
	}

	for _, attr := range h.attrs {
		obj.Set(attr.Key, safeJsValueOf(attr.Value))
	}

	return obj, root
}

func (h *BrowserConsoleLogHandler) Handle(ctx context.Context, record slog.Record) error {
	console := js.Global().Get("console")

	var method string
	switch record.Level {
	case slog.LevelDebug:
		method = "debug"
	case slog.LevelInfo:
		method = "info"
	case slog.LevelWarn:
		method = "warn"
	case slog.LevelError:
		method = "error"
	}

	message := record.Message + "\n"

	attrs, attrsRoot := h.getAttrsObject()

	record.Attrs(func(attr slog.Attr) bool {
		attrs.Set(attr.Key, safeJsValueOf(attr.Value))
		return true
	})

	properties := js.Global().Get("Object").Call("keys", attrsRoot).Get("length")
	if properties.Equal(js.ValueOf(0)) {
		console.Call(method, message)
	} else {
		console.Call(method, message, attrsRoot)
	}

	return nil
}

func (h *BrowserConsoleLogHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
	return &BrowserConsoleLogHandler{
		attrs:  attrs,
		group:  "",
		parent: h,
	}
}

func (h *BrowserConsoleLogHandler) WithGroup(name string) slog.Handler {
	if name == "" {
		return h
	}

	return &BrowserConsoleLogHandler{
		attrs:  nil,
		group:  name,
		parent: h,
	}
}