import { Component, ComponentInterface, Element, Event, EventEmitter, Host, Prop, Watch, h } from '@stencil/core';

import { getIonMode } from '../../global/ionic-global';
import { Gesture, GestureDetail, PickerColumn } from '../../interface';
import { hapticSelectionChanged } from '../../utils/haptic';
import { clamp } from '../../utils/helpers';

/**
 * @internal
 */
@Component({
  tag: 'ion-picker-column',
  styleUrls: {
    ios: 'picker-column.ios.scss',
    md: 'picker-column.md.scss'
  }
})
export class PickerColumnCmp implements ComponentInterface {

  private bounceFrom!: number;
  private lastIndex?: number;
  private minY!: number;
  private maxY!: number;
  private optHeight = 0;
  private rotateFactor = 0;
  private scaleFactor = 1;
  private velocity = 0;
  private y = 0;
  private optsEl?: HTMLElement;
  private gesture?: Gesture;
  private rafId: any;
  private tmrId: any;
  private noAnimate = true;

  @Element() el!: HTMLElement;

  /**
   * Emitted when the selected value has changed
   * @internal
   */
  @Event() ionPickerColChange!: EventEmitter<PickerColumn>;

  /** Picker column data */
  @Prop() col!: PickerColumn;
  @Watch('col')
  protected colChanged() {
    this.refresh();
  }

  async connectedCallback() {
    let pickerRotateFactor = 0;
    let pickerScaleFactor = 0.81;

    const mode = getIonMode(this);

    if (mode === 'ios') {
      pickerRotateFactor = -0.46;
      pickerScaleFactor = 1;
    }

    this.rotateFactor = pickerRotateFactor;
    this.scaleFactor = pickerScaleFactor;

    this.gesture = (await import('../../utils/gesture')).createGesture({
      el: this.el,
      gestureName: 'picker-swipe',
      gesturePriority: 100,
      threshold: 0,
      onStart: ev => this.onStart(ev),
      onMove: ev => this.onMove(ev),
      onEnd: ev => this.onEnd(ev),
    });
    this.gesture.enable();
    this.tmrId = setTimeout(() => {
      this.noAnimate = false;
      this.refresh(true);
    }, 250);
  }

  componentDidLoad() {
    const colEl = this.optsEl;
    if (colEl) {
      // DOM READ
      // We perfom a DOM read over a rendered item, this needs to happen after the first render
      this.optHeight = (colEl.firstElementChild ? colEl.firstElementChild.clientHeight : 0);
    }

    this.refresh();
  }

  disconnectedCallback() {
    cancelAnimationFrame(this.rafId);
    clearTimeout(this.tmrId);
    if (this.gesture) {
      this.gesture.destroy();
      this.gesture = undefined;
    }
  }

  private emitColChange() {
    this.ionPickerColChange.emit(this.col);
  }

  private setSelected(selectedIndex: number, duration: number) {
    // if there is a selected index, then figure out it's y position
    // if there isn't a selected index, then just use the top y position
    const y = (selectedIndex > -1) ? -(selectedIndex * this.optHeight) : 0;

    this.velocity = 0;

    // set what y position we're at
    cancelAnimationFrame(this.rafId);
    this.update(y, duration, true);

    this.emitColChange();
  }

  private update(y: number, duration: number, saveY: boolean) {
    if (!this.optsEl) {
      return;
    }

    // ensure we've got a good round number :)
    let translateY = 0;
    let translateZ = 0;
    const { col, rotateFactor } = this;
    const selectedIndex = col.selectedIndex = this.indexForY(-y);
    const durationStr = (duration === 0) ? '' : duration + 'ms';
    const scaleStr = `scale(${this.scaleFactor})`;

    const children = this.optsEl.children;
    for (let i = 0; i < children.length; i++) {
      const button = children[i] as HTMLElement;
      const opt = col.options[i];
      const optOffset = (i * this.optHeight) + y;
      let transform = '';

      if (rotateFactor !== 0) {
        const rotateX = optOffset * rotateFactor;
        if (Math.abs(rotateX) <= 90) {
          translateY = 0;
          translateZ = 90;
          transform = `rotateX(${rotateX}deg) `;
        } else {
          translateY = -9999;
        }

      } else {
        translateZ = 0;
        translateY = optOffset;
      }

      const selected = selectedIndex === i;
      transform += `translate3d(0px,${translateY}px,${translateZ}px) `;
      if (this.scaleFactor !== 1 && !selected) {
        transform += scaleStr;
      }

      // Update transition duration
      if (this.noAnimate) {
        opt.duration = 0;
        button.style.transitionDuration = '';

      } else if (duration !== opt.duration) {
        opt.duration = duration;
        button.style.transitionDuration = durationStr;
      }

      // Update transform
      if (transform !== opt.transform) {
        opt.transform = transform;
        button.style.transform = transform;
      }
      // Update selected item
      if (selected !== opt.selected) {
        opt.selected = selected;
        if (selected) {
          button.classList.add(PICKER_OPT_SELECTED);
        } else {
          button.classList.remove(PICKER_OPT_SELECTED);
        }
      }
    }
    this.col.prevSelected = selectedIndex;

    if (saveY) {
      this.y = y;
    }

    if (this.lastIndex !== selectedIndex) {
      // have not set a last index yet
      hapticSelectionChanged();
      this.lastIndex = selectedIndex;
    }
  }

  private decelerate() {
    if (this.velocity !== 0) {
      // still decelerating
      this.velocity *= DECELERATION_FRICTION;

      // do not let it go slower than a velocity of 1
      this.velocity = (this.velocity > 0)
        ? Math.max(this.velocity, 1)
        : Math.min(this.velocity, -1);

      let y = this.y + this.velocity;

      if (y > this.minY) {
        // whoops, it's trying to scroll up farther than the options we have!
        y = this.minY;
        this.velocity = 0;

      } else if (y < this.maxY) {
        // gahh, it's trying to scroll down farther than we can!
        y = this.maxY;
        this.velocity = 0;
      }

      this.update(y, 0, true);
      const notLockedIn = (Math.round(y) % this.optHeight !== 0) || (Math.abs(this.velocity) > 1);
      if (notLockedIn) {
        // isn't locked in yet, keep decelerating until it is
        this.rafId = requestAnimationFrame(() => this.decelerate());
      } else {
        this.velocity = 0;
        this.emitColChange();
      }

    } else if (this.y % this.optHeight !== 0) {
      // needs to still get locked into a position so options line up
      const currentPos = Math.abs(this.y % this.optHeight);

      // create a velocity in the direction it needs to scroll
      this.velocity = (currentPos > (this.optHeight / 2) ? 1 : -1);

      this.decelerate();
    }
  }

  private indexForY(y: number) {
    return Math.min(Math.max(Math.abs(Math.round(y / this.optHeight)), 0), this.col.options.length - 1);
  }

  // TODO should this check disabled?

  private onStart(detail: GestureDetail) {
    // We have to prevent default in order to block scrolling under the picker
    // but we DO NOT have to stop propagation, since we still want
    // some "click" events to capture
    detail.event.preventDefault();
    detail.event.stopPropagation();

    // reset everything
    cancelAnimationFrame(this.rafId);
    const options = this.col.options;
    let minY = (options.length - 1);
    let maxY = 0;
    for (let i = 0; i < options.length; i++) {
      if (!options[i].disabled) {
        minY = Math.min(minY, i);
        maxY = Math.max(maxY, i);
      }
    }

    this.minY = -(minY * this.optHeight);
    this.maxY = -(maxY * this.optHeight);
  }

  private onMove(detail: GestureDetail) {
    detail.event.preventDefault();
    detail.event.stopPropagation();

    // update the scroll position relative to pointer start position
    let y = this.y + detail.deltaY;

    if (y > this.minY) {
      // scrolling up higher than scroll area
      y = Math.pow(y, 0.8);
      this.bounceFrom = y;

    } else if (y < this.maxY) {
      // scrolling down below scroll area
      y += Math.pow(this.maxY - y, 0.9);
      this.bounceFrom = y;

    } else {
      this.bounceFrom = 0;
    }

    this.update(y, 0, false);
  }

  private onEnd(detail: GestureDetail) {
    if (this.bounceFrom > 0) {
      // bounce back up
      this.update(this.minY, 100, true);
      this.emitColChange();
      return;
    } else if (this.bounceFrom < 0) {
      // bounce back down
      this.update(this.maxY, 100, true);
      this.emitColChange();
      return;
    }

    this.velocity = clamp(-MAX_PICKER_SPEED, detail.velocityY * 23, MAX_PICKER_SPEED);
    if (this.velocity === 0 && detail.deltaY === 0) {
      const opt = (detail.event.target as Element).closest('.picker-opt');
      if (opt && opt.hasAttribute('opt-index')) {
        this.setSelected(parseInt(opt.getAttribute('opt-index')!, 10), TRANSITION_DURATION);
      }

    } else {
      this.y += detail.deltaY;

      if (Math.abs(detail.velocityY) < 0.05) {
        const isScrollingUp = detail.deltaY > 0;
        const optHeightFraction = (Math.abs(this.y) % this.optHeight) / this.optHeight;

        if (isScrollingUp && optHeightFraction > 0.5) {
          this.velocity = Math.abs(this.velocity) * -1;
        } else if (!isScrollingUp && optHeightFraction <= 0.5) {
          this.velocity = Math.abs(this.velocity);
        }
      }

      this.decelerate();
    }
  }

  private refresh(forceRefresh?: boolean) {
    let min = this.col.options.length - 1;
    let max = 0;
    const options = this.col.options;
    for (let i = 0; i < options.length; i++) {
      if (!options[i].disabled) {
        min = Math.min(min, i);
        max = Math.max(max, i);
      }
    }

    /**
     * Only update selected value if column has a
     * velocity of 0. If it does not, then the
     * column is animating might land on
     * a value different than the value at
     * selectedIndex
     */
    if (this.velocity !== 0) { return; }

    const selectedIndex = clamp(min, this.col.selectedIndex || 0, max);
    if (this.col.prevSelected !== selectedIndex || forceRefresh) {
      const y = (selectedIndex * this.optHeight) * -1;
      this.velocity = 0;
      this.update(y, TRANSITION_DURATION, true);
    }
  }

  render() {
    const col = this.col;
    const Button = 'button' as any;
    const mode = getIonMode(this);
    return (
      <Host
        class={{
          [mode]: true,
          'picker-col': true,
          'picker-opts-left': this.col.align === 'left',
          'picker-opts-right': this.col.align === 'right'
        }}
        style={{
          'max-width': this.col.columnWidth
        }}
      >
        {col.prefix && (
          <div class="picker-prefix" style={{ width: col.prefixWidth! }}>
            {col.prefix}
          </div>
        )}
        <div
          class="picker-opts"
          style={{ maxWidth: col.optionsWidth! }}
          ref={el => this.optsEl = el}
        >
          { col.options.map((o, index) =>
            <Button
              type="button"
              class={{ 'picker-opt': true, 'picker-opt-disabled': !!o.disabled }}
              opt-index={index}
            >
              {o.text}
            </Button>
          )}
        </div>
        {col.suffix && (
          <div class="picker-suffix" style={{ width: col.suffixWidth! }}>
            {col.suffix}
          </div>
        )}
      </Host>
    );
  }
}

const PICKER_OPT_SELECTED = 'picker-opt-selected';
const DECELERATION_FRICTION = 0.97;
const MAX_PICKER_SPEED = 90;
const TRANSITION_DURATION = 150;
