import type { LinkEntity, MentionEntity, TagEntity } from "../core";
import type {
  AngularContentEllipsisConfig,
  AngularCountEllipsisConfig,
  AngularLinkRenderer,
  AngularRenderResult,
  AngularRowsEllipsisConfig,
  AngularTagRenderer,
  AngularMentionRenderer,
} from "./types";

import { NgFor, NgIf, NgSwitch, NgSwitchCase, NgSwitchDefault } from "@angular/common";
import {
  AfterViewInit,
  ChangeDetectionStrategy,
  ChangeDetectorRef,
  Component,
  ElementRef,
  EventEmitter,
  Input,
  OnChanges,
  OnDestroy,
  Output,
  SimpleChanges,
  ViewChild,
} from "@angular/core";

import {
  TachTypographyComponent,
  type TachTypographyHostProps,
} from "@hublib-web/tach-typography/angular";
import type { TypographyWeight } from "@hublib-web/tach-typography/core";

import { findAllEntities } from "../core";
import { ContentSuggestionsRenderResultDirective } from "./render-result.directive";

const READ_MORE_TEXT = "Читать полностью";
const BODY_DATA_ATTR = "data-content-suggestions-body";

const BASE_SELECTABLE_STYLE: Record<string, string> = {
  whiteSpace: "pre-wrap",
  WebkitTouchCallout: "default",
  WebkitUserSelect: "text",
  KhtmlUserSelect: "text",
  MozUserSelect: "text",
  msUserSelect: "text",
  userSelect: "text",
};

const BLUR_STYLE: Record<string, string> = {
  filter: "blur(3px)",
  WebkitUserSelect: "none",
  KhtmlUserSelect: "none",
  MozUserSelect: "none",
  msUserSelect: "none",
  userSelect: "none",
  pointerEvents: "none",
};

type TextPart = {
  kind: "text";
  key: string;
  text: string;
};

type MentionPart = {
  kind: "mention";
  key: string;
  entity: MentionEntity;
  index: number;
  customRender: AngularRenderResult | null;
};

type TagPart = {
  kind: "tag";
  key: string;
  entity: TagEntity;
  index: number;
  customRender: AngularRenderResult | null;
};

type LinkPart = {
  kind: "link";
  key: string;
  entity: LinkEntity;
  index: number;
  customRender: AngularRenderResult | null;
};

type ContentPart = TextPart | MentionPart | TagPart | LinkPart;

@Component({
  selector: "content-text",
  standalone: true,
  imports: [
    NgFor,
    NgIf,
    NgSwitch,
    NgSwitchCase,
    NgSwitchDefault,
    TachTypographyComponent,
    ContentSuggestionsRenderResultDirective,
  ],
  changeDetection: ChangeDetectionStrategy.OnPush,
  template: `
    <div #container>
      <tach-typography
        as="p"
        variant="Body"
        [weight]="weight"
        [className]="className"
        [preserveStyle]="mergedStyle"
        [ellipsis]="rowsEllipsis"
        [hostProps]="paragraphHostProps"
      >
        <ng-container *ngFor="let part of visibleParts; trackBy: trackByKey">
          <ng-container [ngSwitch]="part.kind">
            <ng-container *ngSwitchCase="'text'">{{ part.text }}</ng-container>

            <ng-container *ngSwitchCase="'mention'">
              <ng-container *ngIf="part.customRender !== null; else contentSuggestionsDefaultMention">
                <span [contentSuggestionsRenderResult]="part.customRender"></span>
              </ng-container>
              <ng-template #contentSuggestionsDefaultMention>
                <tach-typography as="span" variant="Body" color="link" [weight]="weight">
                  {{ part.entity.displayText }}
                </tach-typography>
              </ng-template>
            </ng-container>

            <ng-container *ngSwitchCase="'tag'">
              <ng-container *ngIf="part.customRender !== null; else contentSuggestionsDefaultTag">
                <span [contentSuggestionsRenderResult]="part.customRender"></span>
              </ng-container>
              <ng-template #contentSuggestionsDefaultTag>
                <tach-typography as="span" variant="Body" color="link" [weight]="weight">
                  {{ part.entity.text }}
                </tach-typography>
              </ng-template>
            </ng-container>

            <ng-container *ngSwitchCase="'link'">
              <ng-container *ngIf="part.customRender !== null; else contentSuggestionsDefaultLink">
                <span [contentSuggestionsRenderResult]="part.customRender"></span>
              </ng-container>
              <ng-template #contentSuggestionsDefaultLink>
                <tach-typography
                  as="a"
                  variant="Body"
                  color="link"
                  [weight]="weight"
                  [hostProps]="buildDefaultLinkHostProps(part.entity.url)"
                >
                  {{ part.entity.text }}
                </tach-typography>
              </ng-template>
            </ng-container>

            <ng-container *ngSwitchDefault></ng-container>
          </ng-container>
        </ng-container>

        <ng-container *ngIf="showTrailingEllipsis">…</ng-container>

        <button
          *ngIf="showInlineReadMore"
          type="button"
          (click)="handleExpand($event)"
          style="border: 0; background: none; padding: 0; margin-left: 6px; cursor: pointer;"
        >
          <tach-typography as="span" variant="Body" color="link" weight="bold">
            {{ readMoreLabel }}
          </tach-typography>
        </button>
      </tach-typography>

      <button
        *ngIf="showBlockReadMore"
        type="button"
        (click)="handleExpand($event)"
        style="border: 0; background: none; padding: 0; margin-top: 6px; cursor: pointer;"
      >
        <tach-typography as="span" variant="Body" color="link" weight="bold">
          {{ readMoreLabel }}
        </tach-typography>
      </button>
    </div>
  `,
})
export class ContentTextComponent implements OnChanges, AfterViewInit, OnDestroy {
  @Input() className: string | undefined;
  @Input() weight: TypographyWeight = "normal";
  @Input() text: string | null | undefined;
  @Input() ellipsis: AngularContentEllipsisConfig = false;
  @Input() blur = false;
  @Input() style: Record<string, string | number> | null | undefined;
  @Input() onView: (() => void) | undefined;
  @Input() renderMention: AngularMentionRenderer | undefined;
  @Input() renderTag: AngularTagRenderer | undefined;
  @Input() renderLink: AngularLinkRenderer | undefined;

  @Output() readonly viewed = new EventEmitter<void>();
  @Output() readonly expandedChange = new EventEmitter<boolean>();

  @ViewChild("container", { static: true })
  private readonly containerRef!: ElementRef<HTMLElement>;

  visibleParts: ContentPart[] = [];
  mergedStyle: Record<string, string | number> = { ...BASE_SELECTABLE_STYLE };
  rowsEllipsis: { rows: number } | undefined;
  showTrailingEllipsis = false;
  showInlineReadMore = false;
  showBlockReadMore = false;
  readMoreLabel = READ_MORE_TEXT;
  paragraphHostProps: TachTypographyHostProps = { [BODY_DATA_ATTR]: "true" };

  private expanded = false;
  private mergedExpanded = false;
  private isExpandedControlled = false;
  private isInsideView = false;
  private viewedFired = false;
  private pendingRowsOverflowCheck = false;
  private intersectionObserver: IntersectionObserver | null = null;

  constructor(
    private readonly cdr: ChangeDetectorRef,
  ) {}

  ngOnChanges(_changes: SimpleChanges): void {
    this.recomputeContent();
  }

  ngAfterViewInit(): void {
    this.initObserver();
    this.scheduleRowsOverflowCheck();
  }

  ngOnDestroy(): void {
    if (this.intersectionObserver) {
      this.intersectionObserver.disconnect();
      this.intersectionObserver = null;
    }
  }

  trackByKey(_index: number, part: ContentPart): string {
    return part.key;
  }

  buildDefaultLinkHostProps(url: string): TachTypographyHostProps {
    return {
      href: url,
      target: "_blank",
      referrerPolicy: "no-referrer",
    };
  }

  handleExpand(event: MouseEvent): void {
    event.preventDefault();
    event.stopPropagation();

    if (!this.isExpandedControlled) {
      this.expanded = true;
    }

    this.notifyExpand(event, true);
    this.recomputeContent();
  }

  private recomputeContent(): void {
    const content = this.text ?? "";
    const entities = findAllEntities(content);
    const ellipsisConfig = this.resolveEllipsisConfig();

    this.isExpandedControlled = Boolean(
      ellipsisConfig && typeof ellipsisConfig.expanded === "boolean",
    );

    if (!this.isExpandedControlled && this.isCountConfig(ellipsisConfig)) {
      const count = ellipsisConfig.count ?? 0;
      if (content.length <= count && !this.expanded) {
        this.expanded = true;
      }
    }

    this.mergedExpanded = this.getMergedExpanded(ellipsisConfig, content);
    this.readMoreLabel = this.resolveEllipsisSymbol(
      ellipsisConfig?.symbol,
      this.mergedExpanded,
    );

    this.mergedStyle = {
      ...BASE_SELECTABLE_STYLE,
      ...(this.blur ? BLUR_STYLE : {}),
      ...(this.style ?? {}),
    };

    this.visibleParts = this.buildParts(content, entities, null);
    this.rowsEllipsis = undefined;
    this.showTrailingEllipsis = false;
    this.showInlineReadMore = false;
    this.showBlockReadMore = false;
    this.pendingRowsOverflowCheck = false;

    if (this.isCountConfig(ellipsisConfig)) {
      const count = ellipsisConfig.count ?? 0;
      const shouldTruncate = !this.mergedExpanded && count > 0 && content.length > count;

      if (shouldTruncate) {
        const cutoff = this.computeEntitySafeCutoff(count, entities);
        this.visibleParts = this.buildParts(content, entities, cutoff);
        this.showTrailingEllipsis = true;
        this.showInlineReadMore = Boolean(ellipsisConfig.expandable);
      }
    } else if (this.isRowsConfig(ellipsisConfig) && !this.mergedExpanded) {
      this.rowsEllipsis = {
        rows: ellipsisConfig.rows,
      };

      if (ellipsisConfig.expandable) {
        this.pendingRowsOverflowCheck = true;
      }
    }

    this.emitViewIfNeeded();
    this.scheduleRowsOverflowCheck();
    this.cdr.markForCheck();
  }

  private buildParts(
    content: string,
    entities: ReturnType<typeof findAllEntities>,
    upto: number | null,
  ): ContentPart[] {
    const parts: ContentPart[] = [];
    let lastIndex = 0;

    for (const [index, entity] of entities.entries()) {
      if (upto !== null && entity.start >= upto) {
        break;
      }

      const textEnd = upto !== null ? Math.min(entity.start, upto) : entity.start;
      if (entity.start > lastIndex && lastIndex < textEnd) {
        parts.push({
          kind: "text",
          key: `text-${lastIndex}-${textEnd}`,
          text: content.slice(lastIndex, textEnd),
        });
      }

      if (upto === null || entity.end <= upto) {
        if (entity.type === "mention") {
          parts.push({
            kind: "mention",
            key: `mention-${entity.start}-${index}`,
            entity,
            index,
            customRender: this.resolveCustomRender(this.renderMention, entity, index),
          });
        } else if (entity.type === "tag") {
          parts.push({
            kind: "tag",
            key: `tag-${entity.start}-${index}`,
            entity,
            index,
            customRender: this.resolveCustomRender(this.renderTag, entity, index),
          });
        } else {
          parts.push({
            kind: "link",
            key: `link-${entity.start}-${index}`,
            entity,
            index,
            customRender: this.resolveCustomRender(this.renderLink, entity, index),
          });
        }
      }

      lastIndex = entity.end;
    }

    if (upto === null) {
      if (lastIndex < content.length) {
        parts.push({
          kind: "text",
          key: `text-${lastIndex}-${content.length}`,
          text: content.slice(lastIndex),
        });
      }
    } else if (lastIndex < upto) {
      parts.push({
        kind: "text",
        key: `text-${lastIndex}-${upto}`,
        text: content.slice(lastIndex, upto),
      });
    }

    return parts;
  }

  private resolveCustomRender<T>(
    rendererFn: ((entity: T, index: number) => AngularRenderResult) | undefined,
    entity: T,
    index: number,
  ): AngularRenderResult | null {
    const rendered = rendererFn?.(entity, index);
    return rendered ?? null;
  }

  private resolveEllipsisConfig(): AngularCountEllipsisConfig | AngularRowsEllipsisConfig | null {
    if (!this.ellipsis || typeof this.ellipsis !== "object") {
      return null;
    }

    return this.ellipsis;
  }

  private isCountConfig(
    config: AngularCountEllipsisConfig | AngularRowsEllipsisConfig | null,
  ): config is AngularCountEllipsisConfig {
    return Boolean(config && "count" in config);
  }

  private isRowsConfig(
    config: AngularCountEllipsisConfig | AngularRowsEllipsisConfig | null,
  ): config is AngularRowsEllipsisConfig {
    return Boolean(config && "rows" in config);
  }

  private getMergedExpanded(
    config: AngularCountEllipsisConfig | AngularRowsEllipsisConfig | null,
    text: string,
  ): boolean {
    const controlledExpanded =
      config && typeof config.expanded === "boolean"
        ? config.expanded
        : undefined;

    if (controlledExpanded !== undefined) {
      return controlledExpanded;
    }

    if (this.isCountConfig(config)) {
      const count = config.count ?? 0;
      if (count <= 0 || text.length <= count) {
        return true;
      }
    }

    return this.expanded;
  }

  private resolveEllipsisSymbol(
    symbol: AngularCountEllipsisConfig["symbol"] | AngularRowsEllipsisConfig["symbol"],
    expanded: boolean,
  ): string {
    if (typeof symbol === "function") {
      return symbol(expanded);
    }

    return symbol ?? READ_MORE_TEXT;
  }

  private notifyExpand(event: MouseEvent, expanded: boolean): void {
    const config = this.resolveEllipsisConfig();
    const onExpand = config?.onExpand;

    if (onExpand) {
      if (onExpand.length >= 2) {
        (onExpand as (e: MouseEvent, info: { expanded: boolean }) => void)(event, { expanded });
      } else {
        (onExpand as (nextExpanded: boolean) => void)(expanded);
      }
    }

    this.expandedChange.emit(expanded);
  }

  private computeEntitySafeCutoff(
    count: number,
    entities: ReturnType<typeof findAllEntities>,
  ): number {
    let cutoff = count;
    let extended = true;

    while (extended) {
      extended = false;

      for (const entity of entities) {
        if (entity.start < cutoff && entity.end > cutoff) {
          cutoff = entity.end;
          extended = true;
        }
      }
    }

    return cutoff;
  }

  private initObserver(): void {
    const host = this.containerRef?.nativeElement;
    if (!host) {
      return;
    }

    if (typeof IntersectionObserver === "undefined") {
      this.isInsideView = true;
      this.emitViewIfNeeded();
      return;
    }

    this.intersectionObserver = new IntersectionObserver(
      entries => {
        const entry = entries[0];
        if (!entry) {
          return;
        }

        if (entry.isIntersecting && !this.isInsideView) {
          this.isInsideView = true;
          this.emitViewIfNeeded();
        }
      },
      { threshold: 0.5 },
    );

    this.intersectionObserver.observe(host);
  }

  private emitViewIfNeeded(): void {
    if (!this.mergedExpanded || this.viewedFired || !this.isInsideView) {
      return;
    }

    this.viewedFired = true;
    this.onView?.();
    this.viewed.emit();
  }

  private scheduleRowsOverflowCheck(): void {
    if (!this.pendingRowsOverflowCheck) {
      return;
    }

    queueMicrotask(() => {
      this.refreshRowsOverflow();
    });
  }

  private refreshRowsOverflow(): void {
    const paragraph = this.getParagraphElement();
    if (!paragraph) {
      return;
    }

    const hasOverflow = paragraph.scrollHeight - paragraph.clientHeight > 1;
    if (this.showBlockReadMore !== hasOverflow) {
      this.showBlockReadMore = hasOverflow;
      this.cdr.markForCheck();
    }
  }

  private getParagraphElement(): HTMLElement | null {
    const host = this.containerRef?.nativeElement;
    if (!host) {
      return null;
    }

    return host.querySelector(`[${BODY_DATA_ATTR}="true"]`);
  }
}