import {
  EditorView,
  showTooltip,
  Tooltip,
  TooltipView,
  keymap,
} from '@codemirror/view'
import {
  Extension,
  StateField,
  StateEffect,
  TransactionSpec,
  EditorSelection,
  Prec,
} from '@codemirror/state'

export const openContextMenuEffect = StateEffect.define<{
  pos: number
  x: number
  y: number
}>()

export const closeContextMenuEffect = StateEffect.define()

type ContextMenuState = {
  tooltip: Tooltip | null
  mousePosition: { x: number; y: number } | null
}

export const contextMenuStateField = StateField.define<ContextMenuState>({
  create() {
    return { tooltip: null, mousePosition: null }
  },

  update(field, tr) {
    // Process state effects to open/close menu
    for (const effect of tr.effects) {
      if (effect.is(openContextMenuEffect)) {
        const { pos, x, y } = effect.value
        return {
          tooltip: buildContextMenuTooltip(pos),
          mousePosition: { x, y },
        }
      }
      if (effect.is(closeContextMenuEffect)) {
        return { tooltip: null, mousePosition: null }
      }
    }

    // Close menu on document changes
    if (tr.docChanged && field.tooltip) {
      return { tooltip: null, mousePosition: null }
    }

    return field
  },

  // Connect state field to tooltip system
  provide: field => [
    showTooltip.compute([field], state => state.field(field).tooltip),
  ],
})

function buildContextMenuTooltip(pos: number): Tooltip {
  return {
    pos,
    above: false,
    strictSide: false,
    arrow: false,
    create: createTooltipView,
  }
}

const createTooltipView = (): TooltipView => {
  const dom = document.createElement('div')
  dom.className = 'editor-context-menu-container'
  return { dom, overlap: true, offset: { x: 0, y: 0 } }
}

function isPositionInsideSelection(pos: number, from: number, to: number) {
  return from !== to && pos >= from && pos <= to
}

function isPositionInsideAnyRangeOrCursor(view: EditorView, pos: number) {
  for (const range of view.state.selection.ranges) {
    // If it's a cursor, treat a right-click anywhere on the same line as "inside".
    // This avoids collapsing multi-cursor selections when right-clicking on blank lines
    // or to the right of the caret.
    if (range.from === range.to) {
      const clickedLine = view.state.doc.lineAt(pos)
      const cursorLine = view.state.doc.lineAt(range.from)
      if (clickedLine.number === cursorLine.number) {
        return true
      }
      continue
    }

    if (isPositionInsideSelection(pos, range.from, range.to)) {
      return true
    }
  }
  return false
}

function selectEntireLine(
  view: EditorView,
  pos: number
): EditorSelection | null {
  if (pos === null) {
    return null
  }

  const line = view.state.doc.lineAt(pos)
  return EditorSelection.single(line.from, line.to)
}

function closeContextMenu(view: EditorView): void {
  const menuState = view.state.field(contextMenuStateField, false)
  if (menuState?.tooltip) {
    view.dispatch({ effects: closeContextMenuEffect.of(null) })
  }
}

function openContextMenuAtPosition(
  view: EditorView,
  pos: number,
  selection: EditorSelection | TransactionSpec['selection'],
  clientX: number,
  clientY: number
): void {
  view.dispatch({
    selection,
    effects: openContextMenuEffect.of({
      pos,
      x: clientX,
      y: clientY,
    }),
  })
}

function isClickOnGutter(target: HTMLElement): boolean {
  return !!target.closest('.cm-gutters')
}

// Gutter context menu plugin
const gutterContextMenuPlugin = (): Extension =>
  EditorView.updateListener.of(update => {
    if (!update.view.dom.parentElement) {
      return
    }

    const gutters = update.view.dom.parentElement.querySelector('.cm-gutters')
    // Attach listener only once per editor instance
    if (!gutters || gutters.hasAttribute('data-context-menu-attached')) {
      return
    }

    gutters.setAttribute('data-context-menu-attached', 'true')
    gutters.addEventListener('contextmenu', (event: Event) => {
      const mouseEvent = event as MouseEvent
      event.preventDefault()

      const pos = update.view.posAtCoords({
        x: mouseEvent.clientX,
        y: mouseEvent.clientY,
      })
      if (pos === null) {
        return
      }

      const selection = selectEntireLine(update.view, pos)
      if (selection) {
        openContextMenuAtPosition(
          update.view,
          pos,
          selection,
          mouseEvent.clientX,
          mouseEvent.clientY
        )
      }
    })
  })

// Editor view context menu handlers
const editorContextMenuHandlers = (): Extension =>
  EditorView.domEventHandlers({
    contextmenu(event: MouseEvent, view: EditorView) {
      event.preventDefault()

      const pos = view.posAtCoords({ x: event.clientX, y: event.clientY })
      if (pos === null) {
        return false
      }

      const clickedInsideSelection = isPositionInsideAnyRangeOrCursor(view, pos)

      // Set cursor to clicked position if outside selection
      let selection: TransactionSpec['selection'] = { anchor: pos }
      if (clickedInsideSelection) {
        // Keep current selection if inside selection
        // so actions apply to the existing selection
        selection = view.state.selection
      }

      openContextMenuAtPosition(
        view,
        pos,
        selection,
        event.clientX,
        event.clientY
      )
      return true
    },

    mousedown(event: MouseEvent, view: EditorView) {
      const target = event.target as HTMLElement
      const isGutter = isClickOnGutter(target)
      const isRightClick = event.button === 2 || event.ctrlKey

      // Close menu on any click except right-click on non-gutter
      if (!isRightClick || isGutter) {
        closeContextMenu(view)
      }

      // Prevent default on right-click to preserve selection
      if (isRightClick) {
        event.preventDefault()
        return true
      }
      return false
    },
  })

// High-priority keymap to handle Escape before default handlers
const contextMenuKeymap = (): Extension =>
  Prec.high(
    keymap.of([
      {
        key: 'Escape',
        run: view => {
          const menuState = view.state.field(contextMenuStateField, false)
          if (menuState?.tooltip) {
            closeContextMenu(view)
            return true
          }
          return false
        },
      },
    ])
  )

export const contextMenu = (enabled: boolean): Extension =>
  enabled
    ? [
        contextMenuContainerTheme,
        contextMenuStateField,
        gutterContextMenuPlugin(),
        editorContextMenuHandlers(),
        contextMenuKeymap(),
      ]
    : []

const contextMenuContainerTheme = EditorView.baseTheme({
  '.editor-context-menu-container.cm-tooltip': {
    backgroundColor: 'transparent',
    border: 'none',
    zIndex: 100,
  },
})