import type { EditorState } from "@codemirror/state";
import {
  foldedRanges,
  foldEffect,
  syntaxTree,
  unfoldEffect,
} from "@codemirror/language";
import { Decoration, type EditorView, WidgetType } from "@codemirror/view";
import { decoratorStateField, isCursorInRange, LinkWidget } from "./util.ts";
import type { Client } from "../client.ts";
import {
  frontmatterMailtoRegex,
  frontmatterQuotesRegex,
  frontmatterUrlRegex,
  frontmatterWikiLinkRegex,
} from "../markdown_parser/constants.ts";
import { processWikiLink, type WikiLinkMatch } from "./wiki_link_processor.ts";

class FrontmatterMarkerWidget extends WidgetType {
  constructor(
    private readonly from: number,
    private readonly to: number,
    private readonly folded: boolean,
  ) {
    super();
  }

  toDOM(view: EditorView): HTMLElement {
    const marker = document.createElement("span");
    marker.className = "sb-frontmatter-marker";
    marker.role = "button";
    marker.tabIndex = 0;
    marker.title = this.folded ? "Unfold frontmatter" : "Fold frontmatter";
    marker.setAttribute(
      "aria-label",
      this.folded ? "Unfold frontmatter" : "Fold frontmatter",
    );
    marker.textContent = `${this.folded ? "◂" : "▾"} frontmatter`;

    const toggleFold = (event: Event) => {
      event.preventDefault();
      event.stopPropagation();
      view.dispatch({
        effects: (this.folded ? unfoldEffect : foldEffect).of({
          from: this.from,
          to: this.to,
        }),
      });
      view.focus();
    };

    marker.addEventListener("click", toggleFold);
    marker.addEventListener("keydown", (event) => {
      if (event.key === "Enter" || event.key === " ") {
        toggleFold(event);
      }
    });
    return marker;
  }

  override eq(other: WidgetType): boolean {
    return (
      other instanceof FrontmatterMarkerWidget &&
      other.from === this.from &&
      other.to === this.to &&
      other.folded === this.folded
    );
  }
}

function hasExactFoldedRange(
  state: EditorState,
  from: number,
  to: number,
): boolean {
  const folded = foldedRanges(state).iter();
  while (folded.value) {
    if (folded.from === from && folded.to === to) {
      return true;
    }
    folded.next();
  }
  return false;
}

export function shouldRenderFrontmatterLivePreview({
  state,
  client,
  from,
  to,
}: {
  state: EditorState;
  client: Client;
  from: number;
  to: number;
}): boolean {
  return (
    !client.ui.viewState.uiOptions.markdownSyntaxRendering &&
    !isCursorInRange(state, [from, to])
  );
}

export function frontmatterPlugin(client: Client) {
  return decoratorStateField((state: EditorState) => {
    const widgets: any[] = [];
    const foldRanges = foldedRanges(state);
    const shortWikiLinks = client.config.get("shortWikiLinks", true);

    syntaxTree(state).iterate({
      enter(node) {
        if (node.name === "FrontMatterMarker") {
          const parent = node.node.parent!;
          const frontmatterFolded = hasExactFoldedRange(
            state,
            parent.from,
            parent.to,
          );

          const folded = foldRanges.iter();
          let shouldShowFrontmatterBanner = false;
          while (folded.value) {
            // Check if cursor is in the folded range
            if (isCursorInRange(state, [folded.from, folded.to])) {
              // console.log("Cursor is in folded area, ");
              shouldShowFrontmatterBanner = true;
              break;
            }
            folded.next();
          }
          if (!isCursorInRange(state, [parent.from, parent.to])) {
            widgets.push(
              Decoration.line({
                class: "sb-line-frontmatter-outside",
              }).range(node.from),
            );
            shouldShowFrontmatterBanner = true;
          }
          if (shouldShowFrontmatterBanner && parent.from === node.from) {
            // Only put this on the first line of the frontmatter
            widgets.push(
              Decoration.widget({
                widget: new FrontmatterMarkerWidget(
                  parent.from,
                  parent.to,
                  frontmatterFolded,
                ),
              }).range(node.from),
            );
          }
        }

        // Render links inside frontmatter code as clickable anchors (external and wiki links)
        if (node.name === "FrontMatterCode") {
          const oFrom = node.from;
          const oTo = node.to;
          const otext = state.sliceDoc(oFrom, oTo);

          let oMatch: RegExpExecArray | null;
          while ((oMatch = frontmatterQuotesRegex.exec(otext)) !== null) {
            const from = oFrom + (oMatch.index ?? 0);
            const to = from + oMatch[0].length;
            const text = state.sliceDoc(from, to);

            // 1) External links: http(s), <scheme>:// URLs
            frontmatterUrlRegex.lastIndex = 0;
            let match: RegExpExecArray | null;
            while ((match = frontmatterUrlRegex.exec(text)) !== null) {
              const mFrom = from + (match.index ?? 0);
              const mTo = mFrom + match[0].length;
              const url = match[1];
              if (
                !shouldRenderFrontmatterLivePreview({
                  state,
                  client,
                  from: mFrom,
                  to: mTo,
                })
              ) {
                continue;
              }
              widgets.push(
                Decoration.replace({
                  widget: new LinkWidget({
                    text: url,
                    title: `Open ${url}`,
                    href: url,
                    cssClass: "sb-external-link",
                    from: mFrom,
                    callback: (e) => {
                      if (e.altKey) {
                        // Move cursor into the link
                        client.editorView.dispatch({
                          selection: { anchor: mFrom },
                        });
                        client.focus();
                        return;
                      }
                      try {
                        // Open http(s) links in a new window/tab, open
                        // alternate schemes in the same page, as they'll
                        // bounce to another application.
                        if (/^https?:\/\//i.test(url)) {
                          globalThis.open(url, "_blank");
                        } else {
                          globalThis.open(url, "_self");
                        }
                      } catch (err) {
                        console.error("Failed to open external link", err);
                      }
                    },
                  }),
                }).range(mFrom, mTo),
              );
            }

            // 2) Internal links: WikiLinks [[...]] (make navigable)
            frontmatterWikiLinkRegex.lastIndex = 0;
            let wMatch: RegExpExecArray | null;
            while ((wMatch = frontmatterWikiLinkRegex.exec(text)) !== null) {
              if (!wMatch || !wMatch.groups) {
                return;
              }
              const mFrom = from + (wMatch.index ?? 0);
              const mTo = mFrom + wMatch[0].length;

              const wikiLinkMatch: WikiLinkMatch = {
                leadingTrivia: wMatch.groups.leadingTrivia,
                stringRef: wMatch.groups.stringRef,
                alias: wMatch.groups.alias,
                trailingTrivia: wMatch.groups.trailingTrivia,
              };

              const decorations = processWikiLink({
                from: mFrom,
                to: mTo,
                match: wikiLinkMatch,
                matchFrom: mFrom,
                matchTo: mTo,
                client,
                shortWikiLinks,
                state,
                callback: (e, ref) => {
                  if (e.altKey) {
                    // Move cursor into the link's content
                    client.editorView.dispatch({
                      selection: {
                        anchor: mFrom + wikiLinkMatch.leadingTrivia.length,
                      },
                    });
                    client.focus();
                    return;
                  }
                  void client.navigate(ref, false, e.ctrlKey || e.metaKey);
                },
              });

              widgets.push(...decorations);
            }

            // 3) mailto:... links
            frontmatterMailtoRegex.lastIndex = 0;
            let mMatch: RegExpExecArray | null;
            while ((mMatch = frontmatterMailtoRegex.exec(text)) !== null) {
              const mFrom = from + (mMatch.index ?? 0);
              const mTo = mFrom + mMatch[0].length;
              const url = mMatch[1];
              const address = url.slice(7);
              if (
                !shouldRenderFrontmatterLivePreview({
                  state,
                  client,
                  from: mFrom,
                  to: mTo,
                })
              ) {
                continue;
              }
              widgets.push(
                Decoration.replace({
                  widget: new LinkWidget({
                    text: url,
                    title: `Mail ${address}`,
                    href: url,
                    cssClass: "sb-external-link",
                    from: mFrom,
                    callback: (e) => {
                      if (e.altKey) {
                        // Move cursor into the link
                        client.editorView.dispatch({
                          selection: { anchor: mFrom },
                        });
                        client.focus();
                        return;
                      }
                      try {
                        globalThis.open(url, "_self");
                      } catch (err) {
                        console.error("Failed to open external link", err);
                      }
                    },
                  }),
                }).range(mFrom, mTo),
              );
            }
          }
        }
      },
    });
    return Decoration.set(widgets, true);
  });
}