import flatpickr from "flatpickr"

import {InputWidget, InputWidgetView} from "@bokehjs/models/widgets/input_widget"
import type {StyleSheetLike} from "@bokehjs/core/dom"
import {bounding_box, input} from "@bokehjs/core/dom"
import {CalendarPosition} from "@bokehjs/core/enums"
import type * as p from "@bokehjs/core/properties"
import {isString} from "@bokehjs/core/util/types"

import * as inputs from "@bokehjs/styles/widgets/inputs.css"
import flatpickr_css from "@bokehjs/styles/widgets/flatpickr.css"

type DateStr = string
type DatesList = (DateStr | [DateStr, DateStr])[]

function _convert_date_list(value: DatesList): flatpickr.Options.DateLimit[] {
  const result: flatpickr.Options.DateLimit[] = []
  for (const item of value) {
    if (isString(item)) {
      result.push(item)
    } else {
      const [from, to] = item
      result.push({from, to})
    }
  }
  return result
}

export class DatetimePickerView extends InputWidgetView {
  declare model: DatetimePicker

  private _picker?: flatpickr.Instance

  override connect_signals(): void {
    super.connect_signals()

    const {
      value, min_date, max_date, disabled_dates, enabled_dates, inline,
      enable_time, enable_seconds, military_time, date_format, mode,
    } = this.model.properties

    this.on_change(value, () => this.model.value ? this._picker?.setDate(this.model.value) : this._clear())
    this.on_change(min_date, () => this._picker?.set("minDate", this.model.min_date))
    this.on_change(max_date, () => this._picker?.set("maxDate", this.model.max_date))
    this.on_change(disabled_dates, () => {
      const {disabled_dates} = this.model
      this._picker?.set("disable", disabled_dates != null ? _convert_date_list(disabled_dates) : [])
    })
    this.on_change(enabled_dates, () => {
      const {enabled_dates} = this.model
      if (enabled_dates != null) {
        this._picker?.set("enable", _convert_date_list(enabled_dates))
      } else {
        // this reimplements `set()` for the `undefined` case
        if (this._picker) {
          this._picker.config._enable = undefined
          this._picker.redraw()
          this._picker.updateValue(true)
        }
      }
    })
    this.on_change(inline, () => this._picker?.set("inline", this.model.inline))
    this.on_change(enable_time, () => this._picker?.set("enableTime", this.model.enable_time))
    this.on_change(enable_seconds, () => this._picker?.set("enableSeconds", this.model.enable_seconds))
    this.on_change(military_time, () => this._picker?.set("time_24hr", this.model.military_time))
    this.on_change(mode, () => this._picker?.set("mode", this.model.mode))
    this.on_change(date_format, () => this._picker?.set("dateFormat", this.model.date_format))
  }

  override remove(): void {
    this._picker?.destroy()
    super.remove()
  }

  override stylesheets(): StyleSheetLike[] {
    return [...super.stylesheets(), flatpickr_css]
  }

  _render_input(): HTMLElement {
    return this.input_el = input({type: "text", class: inputs.input, disabled: this.model.disabled})
  }

  override render(): void {
    if (this._picker != null) {
      return
    }

    super.render()

    const options: flatpickr.Options.Options = {
      appendTo: this.group_el,
      positionElement: this.input_el,
      defaultDate: this.model.value!,
      inline: this.model.inline,
      position: this._position.bind(this),
      enableTime: this.model.enable_time,
      enableSeconds: this.model.enable_seconds,
      time_24hr: this.model.military_time,
      dateFormat: this.model.date_format,
      mode: this.model.mode,
      onClose: (selected_dates, date_string, instance) => this._on_close(selected_dates, date_string, instance),
    }

    const {min_date, max_date, disabled_dates, enabled_dates} = this.model
    if (min_date != null) {
      options.minDate = min_date
    }
    if (max_date != null) {
      options.maxDate = max_date
    }
    if (disabled_dates != null) {
      options.disable = _convert_date_list(disabled_dates)
    }
    if (enabled_dates != null) {
      options.enable = _convert_date_list(enabled_dates)
    }

    this._picker = flatpickr(this.input_el, options)
    this._picker.maxDateHasTime = true
    this._picker.minDateHasTime = true
  }

  protected _clear() {
    this._picker?.clear()
    this.model.value = null
  }

  protected _on_close(_selected_dates: Date[], date_string: string, _instance: flatpickr.Instance): void {
    if (this.model.mode == "range" && !date_string.includes("to")) {
      return
    }
    this.model.value = date_string
    this.change_input()
  }

  protected _position(self: flatpickr.Instance, custom_el: HTMLElement | undefined): void {
    // This function is copied directly from bokehs date_picker
    const positionElement = custom_el ?? self._positionElement

    const calendarHeight = [...self.calendarContainer.children].reduce((acc, child) => acc + bounding_box(child).height, 0)
    const calendarWidth = self.calendarContainer.offsetWidth
    const configPos = this.model.position.split(" ")
    const configPosVertical = configPos[0]
    const configPosHorizontal = configPos.length > 1 ? configPos[1] : null
    // const inputBounds = positionElement.getBoundingClientRect()
    const inputBounds = {
      top: positionElement.offsetTop,
      bottom: positionElement.offsetTop + positionElement.offsetHeight,
      left: positionElement.offsetLeft,
      right: positionElement.offsetLeft + positionElement.offsetWidth,
      width: positionElement.offsetWidth,
    }
    const distanceFromBottom = window.innerHeight - inputBounds.bottom
    const showOnTop =
      configPosVertical === "above" ||
      (configPosVertical !== "below" &&
        distanceFromBottom < calendarHeight &&
        inputBounds.top > calendarHeight)

    // const top =
    //   window.scrollY +
    //   inputBounds.top +
    //   (!showOnTop ? positionElement.offsetHeight + 2 : -calendarHeight - 2)
    const top = self.config.appendTo
      ? inputBounds.top +
        (!showOnTop ? positionElement.offsetHeight + 2 : -calendarHeight - 2)
      : window.scrollY +
        inputBounds.top +
        (!showOnTop ? positionElement.offsetHeight + 2 : -calendarHeight - 2)

    self.calendarContainer.classList.toggle("arrowTop", !showOnTop)
    self.calendarContainer.classList.toggle("arrowBottom", showOnTop)

    if (self.config.inline) {
      return
    }

    let left = window.scrollX + inputBounds.left
    let isCenter = false
    let isRight = false

    if (configPosHorizontal === "center") {
      left -= (calendarWidth - inputBounds.width) / 2
      isCenter = true
    } else if (configPosHorizontal === "right") {
      left -= calendarWidth - inputBounds.width
      isRight = true
    }

    self.calendarContainer.classList.toggle("arrowLeft", !isCenter && !isRight)
    self.calendarContainer.classList.toggle("arrowCenter", isCenter)
    self.calendarContainer.classList.toggle("arrowRight", isRight)

    const right =
      window.document.body.offsetWidth -
      (window.scrollX + inputBounds.right)
    const rightMost = left + calendarWidth > window.document.body.offsetWidth
    const centerMost = right + calendarWidth > window.document.body.offsetWidth

    self.calendarContainer.classList.toggle("rightMost", rightMost)

    if (self.config.static) {
      return
    }

    self.calendarContainer.style.top = `${top}px`

    if (!rightMost) {
      self.calendarContainer.style.left = `${left}px`
      self.calendarContainer.style.right = "auto"
    } else if (!centerMost) {
      self.calendarContainer.style.left = "auto"
      self.calendarContainer.style.right = `${right}px`
    } else {
      const css = this.shadow_el.styleSheets[0]
      const bodyWidth = window.document.body.offsetWidth
      const centerLeft = Math.max(0, bodyWidth / 2 - calendarWidth / 2)
      const centerBefore = ".flatpickr-calendar.centerMost:before"
      const centerAfter = ".flatpickr-calendar.centerMost:after"
      const centerIndex = css.cssRules.length
      const centerStyle = `{left:${inputBounds.left}px;right:auto;}`
      self.calendarContainer.classList.toggle("rightMost", false)
      self.calendarContainer.classList.toggle("centerMost", true)
      css.insertRule(`${centerBefore},${centerAfter}${centerStyle}`, centerIndex)
      self.calendarContainer.style.left = `${centerLeft}px`
      self.calendarContainer.style.right = "auto"
    }
  }
}

export namespace DatetimePicker {
  export type Attrs = p.AttrsOf<Props>

  export type Props = InputWidget.Props & {
    value:          p.Property<string | null>
    min_date:       p.Property<string | null>
    max_date:       p.Property<string | null>
    disabled_dates: p.Property<DatesList | null>
    enabled_dates:  p.Property<DatesList | null>
    position:       p.Property<CalendarPosition>
    inline:         p.Property<boolean>
    enable_time:    p.Property<boolean>
    enable_seconds: p.Property<boolean>
    military_time:  p.Property<boolean>
    date_format:    p.Property<string>
    mode:           p.Property<any>
  }
}

export interface DatetimePicker extends DatetimePicker.Attrs {}

export class DatetimePicker extends InputWidget {
  declare properties: DatetimePicker.Props
  declare __view_type__: DatetimePickerView

  constructor(attrs?: Partial<DatetimePicker.Attrs>) {
    super(attrs)
  }

  static override __module__ = "panel.models.datetime_picker"

  static {
    this.prototype.default_view = DatetimePickerView

    this.define<DatetimePicker.Props>(({Bool, Str, List, Tuple, Or, Nullable}) => {
      const DateStr = Str
      const DatesList = List(Or(DateStr, Tuple(DateStr, DateStr)))
      return {
        value:          [ Nullable(Str), null ],
        min_date:       [ Nullable(Str), null ],
        max_date:       [ Nullable(Str), null ],
        disabled_dates: [ Nullable(DatesList), null ],
        enabled_dates:  [ Nullable(DatesList), null ],
        position:       [ CalendarPosition, "auto" ],
        inline:         [ Bool, false ],
        enable_time:    [ Bool, true ],
        enable_seconds: [ Bool, true ],
        military_time:  [ Bool, true ],
        date_format:    [ Str, "Y-m-d H:i:S" ],
        mode:           [ Str, "single" ],
      }
    })
  }
}