import { existsSync, readFileSync, writeFileSync } from "fs";
import path from "node:path";
import slug from "slug";
import type Vault from "./vault.js";
import {
  combineMarkdownAndFrontmatter,
  extractFrontmatter,
  extractMarkdown,
  extractTags,
  type FrontmatterShape,
} from "./markdown.js";

export default class MarkdownDocument {
  /** A reference to the vault containing this document */
  readonly vault: Vault;

  /** The original file path to this document */
  readonly path: string;

  /** The directory/folder that this Document is in, relative to the vault root */
  readonly dirname: string;

  /** An array of directory names this document is found under */
  readonly taxonomy: string[];

  /** The name of this document's file, without the file extension */
  readonly filename: string;

  /** An array of tags found in this document from both the markdown and frontmatter */
  tags: string[];

  /** A url-safe version of this file's name */
  readonly slug: string;

  /** The raw content of the file */
  private _content: string;

  /** The history of this files contents after each modification */
  readonly contentHistory: string[];

  /** The parsed frontmatter of the file */
  private _frontmatter: FrontmatterShape;

  /** Structured document metadata */
  meta: Record<string, unknown> = {};

  /** The markdown portion of the file (without frontmatter) */
  private _markdown: string;

  constructor(filePath: string, vault: Vault) {
    if (!existsSync(filePath)) {
      throw new Error(`File not found: ${filePath}`);
    }

    const rawFileContent = readFileSync(filePath, "utf-8");
    const fileDirname = path.dirname(filePath);
    const vaultPath = vault.vaultPath;
    const frontmatter = extractFrontmatter(rawFileContent);

    this.path = filePath;
    this.dirname = path.relative(vaultPath, fileDirname);
    this.taxonomy = this.dirname.split(path.sep);
    this.filename = path.basename(filePath, ".md");
    this.slug = slug(this.filename);
    this._content = rawFileContent;
    this.contentHistory = [rawFileContent];
    this._frontmatter = frontmatter;
    this._markdown = extractMarkdown(rawFileContent);
    this.vault = vault;

    const frontmatterTags = frontmatter.tags;
    const contentTags = extractTags(this._markdown);
    this.tags = frontmatterTags.concat(contentTags);
  }

  /**
   * @returns A serializable shape for this object
   */
  toJSON() {
    return {
      path: this.path,
      dirname: this.dirname,
      taxonomy: this.taxonomy,
      filename: this.filename,
      slug: this.slug,
      frontmatter: this._frontmatter,
      markdown: this._markdown,
    };
  }

  /**
   * Update the markdown content for the document
   * @param newValue The new markdown content for the document
   */
  setMarkdown(newValue: string): MarkdownDocument {
    this._markdown = newValue;
    this._content = combineMarkdownAndFrontmatter(newValue, this.frontmatter);
    this.contentHistory.push(this._content);
    return this;
  }

  /**
   * Update the frontmatter of the document
   * @param newValue The new frontmatter shape for this document
   */
  setFrontmatter(newValue: FrontmatterShape): MarkdownDocument {
    this._frontmatter = newValue;
    this._content = combineMarkdownAndFrontmatter(this._markdown, newValue);
    this.contentHistory.push(this._content);
    return this;
  }

  /**
   * Update the full content of the doc with a combination of markdown and yaml frontmatter
   * @param newValue The full content of the document to set
   */
  setContent(newValue: string): MarkdownDocument {
    this._content = newValue;
    this._frontmatter = extractFrontmatter(newValue);
    this._markdown = extractMarkdown(newValue);
    this.contentHistory.push(this._content);
    return this;
  }

  /**
   * Check if this document has a specific tag
   * @param tag The tag to look for
   * @returns `true` If this document has the given tag
   */
  hasTag(tag: string) {
    return this.tags.includes(tag);
  }

  /**
   * Given an array of directory names, return `true` if this document has the taxonomy
   * @param dirs Directories to check for in the taxonomy
   * @returns `true` If this document shares the given taxonomy
   */
  hasTaxonomy(dirs: string[]) {
    if (dirs.length > this.taxonomy.length) {
      return false;
    }

    for (let i = 0; i < dirs.length; i++) {
      if (dirs[i] !== this.taxonomy[i]) {
        return false;
      }
    }

    return true;
  }

  /**
   * Revert this document to its original loaded content
   */
  revert(): MarkdownDocument {
    const originalCopy = this.contentHistory[0];

    if (originalCopy === undefined) {
      throw new Error("Document has no history to revert to.");
    }

    this.setContent(originalCopy);
    return this;
  }

  /**
   * Write this document back to disk
   */
  write(): MarkdownDocument {
    writeFileSync(
      this.path,
      combineMarkdownAndFrontmatter(this._markdown, this.frontmatter),
      "utf-8",
    );

    return this;
  }

  /**
   * Retrieves the value of a frontmatter key as a string.
   * If the key is not found, returns the provided default value.
   * Throws an error if the value is not a string.
   *
   * @param key - The key of the frontmatter value to retrieve.
   * @param defaultValue - The default value to return if the key is not found.
   * @returns The value of the frontmatter key as a string.
   * @throws Error if the frontmatter key is not a string.
   */
  getFrontmatterString(key: string, defaultValue: string): string {
    const val = this._frontmatter[key];

    if (val === undefined) {
      return defaultValue;
    }

    if (typeof val !== "string") {
      throw new Error(`Frontmatter key is not a string: ${key}`);
    }

    return val;
  }

  /**
   * Retrieves an array value from the frontmatter object based on the provided key.
   * If the value is not found, it returns the provided defaultValue.
   * If the value is found but is not an array, it throws an error.
   *
   * @param key - The key to retrieve the array value from the frontmatter object.
   * @param defaultValue - The default value to return if the key is not found in the frontmatter object.
   * @returns The array value associated with the provided key, or the defaultValue if the key is not found.
   * @throws Error if the value associated with the key is found but is not an array.
   */
  getFrontmatterArray(key: string, defaultValue: string[]): string[] {
    const val = this._frontmatter[key];

    if (val === undefined) {
      return defaultValue;
    }

    if (!Array.isArray(val)) {
      throw new Error(`Frontmatter key is not an array: ${key}`);
    }

    return val;
  }

  /** The markdown portion of the file (without frontmatter) */
  get markdown() {
    return this._markdown;
  }

  /** The parsed frontmatter of the file */
  get frontmatter() {
    return this._frontmatter;
  }

  /** The raw content of the file */
  get content() {
    return this._content;
  }
}