/**
 * DOCX exporter (via the `docx` library, v8.x).
 *
 * Builds a WordprocessingML document from the flattened project. Headings,
 * paragraphs, scene breaks, blockquotes, code blocks, lists, and tables are
 * all mapped to native Word elements so the output is editable and re-exportable.
 * The theme supplies fonts, colours, and heading sizes.
 */
import {
  AlignmentType,
  Document,
  Paragraph,
  Packer,
  Table,
  TableCell,
  TableRow,
  TextRun,
  WidthType,
} from "docx";
import type { Block, FlatProject, Mark } from "./model.js";
import { getTheme, type Theme } from "./themes.js";
import { normalizeDocx } from "./determinism.js";

function runToTextRun(run: { text: string; marks: Mark[] }, theme: Theme): TextRun {
  const hasCode = run.marks.some((m) => m.type === "code");
  const hasBold = run.marks.some((m) => m.type === "bold");
  const hasItalic = run.marks.some((m) => m.type === "italic");
  const hasStrike = run.marks.some((m) => m.type === "strike");
  const color = (run.marks.find((m) => m.type === "color")?.attrs?.color as string | undefined) ?? theme.colors.text;
  return new TextRun({
    text: run.text,
    bold: hasBold,
    italics: hasItalic,
    strike: hasStrike,
    font: hasCode ? "Courier New" : theme.fontFamily,
    color,
  });
}

function runsForInline(text: string, marks: Mark[], theme: Theme): TextRun[] {
  if (!marks.length) return [new TextRun({ text, color: theme.colors.text })];
  const boundaries = new Set<number>([0, text.length]);
  for (const m of marks) {
    boundaries.add(Math.max(0, Math.min(text.length, m.start)));
    boundaries.add(Math.max(0, Math.min(text.length, m.end)));
  }
  const points = Array.from(boundaries).sort((a, b) => a - b);
  const runs: TextRun[] = [];
  for (let i = 0; i < points.length - 1; i++) {
    const start = points[i]!;
    const end = points[i + 1]!;
    const runMarks = marks.filter((m) => m.start <= start && m.end >= end);
    runs.push(runToTextRun({ text: text.slice(start, end), marks: runMarks }, theme));
  }
  return runs;
}

function headingLevel(level: number): string {
  if (level <= 1) return "Heading1";
  if (level <= 2) return "Heading2";
  if (level <= 3) return "Heading3";
  if (level <= 4) return "Heading4";
  if (level <= 5) return "Heading5";
  return "Heading6";
}

function blockToParagraph(block: Block, theme: Theme): Paragraph {
  switch (block.type) {
    case "heading": {
      const level = block.level ?? 1;
      return new Paragraph({
        heading: headingLevel(level) as never,
        spacing: { after: 200 },
        children: runsForInline(block.text ?? "", block.marks ?? [], theme),
      }) as unknown as Paragraph;
    }
    case "paragraph":
      return new Paragraph({
        spacing: { after: 200 },
        children: runsForInline(block.text ?? "", block.marks ?? [], theme),
      });
    case "sceneBreak":
      return new Paragraph({
        alignment: AlignmentType.CENTER,
        spacing: { after: 200 },
        children: [new TextRun({ text: "***", italics: true, color: theme.colors.muted })],
      });
    case "blockquote":
      return new Paragraph({
        indent: { left: 360 },
        spacing: { after: 200 },
        children: [
          new TextRun({
            text: (block.children ?? []).map((c) => c.text ?? "").join("\n"),
            italics: true,
            color: theme.colors.muted,
          }),
        ],
      });
    case "codeBlock":
      return new Paragraph({
        spacing: { after: 200 },
        children: [
          new TextRun({
            text: block.text ?? "",
            font: "Courier New",
            size: 16,
            color: theme.colors.text,
          }),
        ],
      });
    case "footnote":
      return new Paragraph({
        indent: { firstLine: 360 },
        spacing: { after: 200 },
        children: [
          new TextRun({ text: block.text ?? "", italics: true, color: theme.colors.muted, size: 18 }),
        ],
      });
    case "list": {
      const items = block.children ?? [];
      const pad = block.listType === "ordered" ? "1. " : "- ";
      return new Paragraph({
        spacing: { after: 120 },
        children: [
          new TextRun({ text: pad, bold: true, color: theme.colors.heading }),
          ...runsForInline(items[0]?.text ?? "", items[0]?.marks ?? [], theme),
        ],
      });
    }
    default:
      return new Paragraph({ spacing: { after: 200 }, children: [] });
  }
}

function buildTable(blocks: Block[], theme: Theme): Table | null {
  const rows = blocks.filter((b) => b.type === "table");
  if (!rows.length) return null;
  const header = rows[0];
  const headers = header?.children ?? [];
  const body = rows.slice(1);
  const headerRow = new TableRow({
    children: headers.map((h) =>
      new TableCell({
        children: [
          new Paragraph({
            children: [
              new TextRun({ text: h.text ?? "", bold: true, color: theme.colors.background }),
            ],
          }),
        ],
      }),
    ),
  });
  const bodyRows = body.map((row) =>
    new TableRow({
      children: (row.children ?? []).map((cell) =>
        new TableCell({
          children: [
            new Paragraph({
              children: [new TextRun({ text: cell.text ?? "" })],
            }),
          ],
        }),
      ),
    }),
  );
  return new Table({
    width: { size: 100, type: WidthType.PERCENTAGE },
    rows: [headerRow, ...bodyRows],
  });
}

export interface DocxOptions {
  themeId?: string;
  generatedAt?: string | undefined;
}

/**
 * Serialize a flattened project to a DOCX (`.docx` bytes).
 *
 * @param project the flattened project (frontmatter + blocks)
 * @param options theme id (defaults to the built-in "ink" theme)
 */
export async function exportDocx(project: FlatProject, options?: DocxOptions): Promise<Uint8Array> {
  const theme = getTheme(options?.themeId);
  const fm = project.frontmatter;

  const children: (Paragraph | Table)[] = [];
  if (fm.title) {
    children.push(
      new Paragraph({
        heading: "Title" as never,
        spacing: { after: 120 },
        children: [new TextRun({ text: fm.title, bold: true, size: 32, color: theme.colors.heading })],
      }) as unknown as Paragraph
    );
  }
  if (fm.author) {
    children.push(
      new Paragraph({
        spacing: { after: 300 },
        children: [new TextRun({ text: fm.author, italics: true, color: theme.colors.muted })],
      })
    );
  }
  for (const block of project.blocks) {
    if (block.type === "table") continue; // handled separately
    children.push(blockToParagraph(block, theme));
  }
  const table = buildTable(project.blocks, theme);
  if (table) children.push(table);

  const doc = new Document({
    sections: [{ children }],
  });

  const buffer = await Packer.toBuffer(doc);
  const generatedAt = options?.generatedAt ?? new Date().toISOString();
  return normalizeDocx(
    new Uint8Array(buffer.buffer, buffer.byteOffset, buffer.byteLength),
    generatedAt
  );
}