import type {
  CSSProperties,
  Component,
  Prop,
  VNodeChild,
} from 'vue'
import { defineComponent, h } from 'vue'
import type {
  Axis,
  Block,
  DataRefer,
  Theme,
  View,
  ViewChildren,
  Widget,
} from './types'
import { provideBlockId } from './context'
import {
  align,
  background,
  bordering,
  clip,
  gap,
  insets,
  radii,
  shadowing,
  size,
  unit,
} from './utils'
import DddView from './views/View.vue'
import DddTextView from './views/TextView.vue'
import DddImageView from './views/ImageView.vue'
import DddAudioView from './views/AudioView.vue'

/**
 * 相关框架组件渲染函数
 */
export type WidgetRenderFunction = (widget: Widget, view: View, axis?: Axis) => VNodeChild

/**
 * 注册的外部组件渲染函数
 */
const widgets: Record<string, WidgetRenderFunction> = {}

const views: Record<string, Component> = {
  text: DddTextView,
  image: DddImageView,
  audio: DddAudioView,
  video: DddAudioView,
}

export function registerWidget(some: Record<string, WidgetRenderFunction>): void {
  for (const [key, func] of Object.entries(some))
    widgets[key] = func
}

function renderWidget(widget: Widget, view: View, axis?: Axis): VNodeChild {
  const func = widgets[widget.name]
  if (typeof func !== 'function')
    throw new Error(`unknown widget: ${widget.name}`)

  return func(widget, view, axis)
}

const isWidget = (s: any): s is Widget => s != null && 'name' in s

function isRefer(s: any): s is DataRefer {
  return s != null
    && 'type' in s
    && 'key' in s
    && typeof s.type === 'string'
    && typeof s.key === 'string'
}

function renderRefer(refer: DataRefer, axis?: Axis): VNodeChild {
  const { key, type, ...attrs } = refer
  const component = views[type]
  if (component) {
    return h(component, {
      source: key,
      axis,
      ...attrs,
    })
  }
  return h('b', {
    style: {
      color: 'red',
      fontSize: '36px',
    },
  }, 'unimplemented')
}

export function isFlexible(theme: Theme) {
  return theme.axis != null
    || theme.mainAlign != null
    || theme.crossAlign != null
    || theme.wrap != null
    || theme.gap != null
}

export function render(view?: ViewChildren, axis?: Axis): VNodeChild {
  if (view == null)
    return null

  if (typeof view === 'string' || typeof view === 'number')
    return view

  if (Array.isArray(view))
    return view.map(v => render(v, axis))

  if (isRefer(view))
    return renderRefer(view)

  if (isWidget(view.theme))
    return renderWidget(view.theme, view, axis)

  const theme = view.theme
  const css: CSSProperties = {
    // boxed & spatial
    ...insets('padding', theme?.padding),
    ...insets('margin', theme?.margin),
    ...size(axis, theme),
    // decoration
    ...background(theme?.color, theme?.image, theme?.gradient),
    ...bordering(theme?.border),
    ...radii(theme?.radius),
    ...shadowing(theme?.shadow),
    // textual
    color: theme?.textColor,
    fontSize: unit(theme?.fontSize),
    textAlign: theme?.textAlign,
    lineHeight: theme?.lineHeight,
    // clip
    ...clip(theme?.clip),
  }

  // note: 在前面初始化 css 时使用了参数 axis，
  // 所以在这里复用它用于子视图构建
  axis = theme?.axis

  if (theme?.flexible || (theme && theme.flexible == null && isFlexible(theme))) {
    Object.assign(css, {
      display: 'flex',
      flexDirection: axis === 'y' ? 'column' : undefined,
      justifyContent: align(theme?.mainAlign),
      alignItems: align(theme?.crossAlign),
      flexWrap: theme?.wrap ? 'wrap' : undefined,
      ...gap(theme?.gap),
    })
  }

  return h(DddView, {
    vid: view.vid,
    class: 'ddd-view',
    style: css,
  }, () => render(view.children, axis))
}

export const RenderBlock = defineComponent({
  name: 'RenderWidget',

  props: {
    block: {
      type: Object,
      required: true,
    } as Prop<Block>,
  },

  setup(props) {
    provideBlockId(props.block!.vid)
    return () => {
      if (props.block == null)
        return null

      return render(props.block)
    }
  },
})