import { Type } from "@earendil-works/pi-ai";
import {
  createReadTool,
  type ExtensionAPI,
  keyHint,
  truncateHead,
  withFileMutationQueue,
} from "@earendil-works/pi-coding-agent";
import { Text } from "@earendil-works/pi-tui";
import { isUtf8 } from "node:buffer";
import { createHash } from "node:crypto";
import { readFile, stat, writeFile } from "node:fs/promises";
import { homedir } from "node:os";
import { resolve } from "node:path";

import anchorData from "./anchor-pieces.json" with { type: "json" };

function filePath(path: string, cwd: string): string {
  return resolve(cwd, path === "~" ? homedir() : path.replace(/^~\//, `${homedir()}/`));
}

function hash(line: string): string {
  const value = createHash("sha256").update(line).digest().readUInt32BE(0);
  const prefixCount = anchorData.prefixes.length / 2;
  const prefix = (value % prefixCount) * 2;
  const suffix = (Math.floor(value / prefixCount) % (anchorData.suffixes.length / 2)) * 2;
  return anchorData.prefixes.slice(prefix, prefix + 2) + anchorData.suffixes.slice(suffix, suffix + 2);
}

async function readText(path: string, signal?: AbortSignal) {
  signal?.throwIfAborted();
  const info = await stat(path);
  if (!info.isFile()) throw new Error("Not a regular file.");
  if (info.size > 50 * 1024 * 1024) throw new Error("File exceeds the 50 MiB edit/read limit.");
  const bytes = await readFile(path, { signal });
  if (!isUtf8(bytes) || bytes.includes(0)) {
    throw new Error("Hashline requires UTF-8 text without NUL bytes.");
  }
  const raw = bytes.toString("utf8");
  const bom = raw.startsWith("\uFEFF") ? "\uFEFF" : "";
  const text = raw.slice(bom.length);
  const rows = text.match(/[^\n]*\n|[^\n]+$/g) ?? [];
  return { raw, bom, text, rows, lines: rows.map((row) => row.replace(/\r?\n$/, "")) };
}

const hashes = Type.Array(Type.String({ pattern: "^[A-Za-z]{4}$" }));

export default function (pi: ExtensionAPI) {
  pi.registerTool({
    name: "read",
    label: "read",
    description:
      "Read UTF-8 text as hash│content, using four-letter tokenizer-friendly hashes of exact line " +
      "content, independent of position. Duplicate lines and hash collisions share anchors; " +
      "use adjacent context with edit to disambiguate them. Supports images with jpg, jpeg, " +
      "png, gif, webp, or bmp extensions. Text output is capped at 2000 lines / 50 KiB; " +
      "use offset/limit to page. Text files over 50 MiB are rejected.",
    promptSnippet: "Read file contents with position-independent content hashes; supports images",
    parameters: Type.Object({
      path: Type.String(),
      offset: Type.Optional(Type.Integer({ minimum: 1, description: "First line (1-indexed)." })),
      limit: Type.Optional(Type.Integer({ minimum: 1, description: "Maximum lines to return." })),
    }),
    async execute(id, args, signal, onUpdate, ctx) {
      const path = filePath(args.path, ctx.cwd);
      if (/\.(jpe?g|png|gif|webp|bmp)$/i.test(path)) {
        return createReadTool(ctx.cwd).execute(id, { ...args, path }, signal, onUpdate);
      }
      const { lines } = await readText(path, signal);
      const start = (args.offset ?? 1) - 1;
      if (start > 0 && start >= lines.length) throw new Error("Offset is beyond end of file.");
      if (!lines.length) {
        return { content: [{ type: "text", text: "[Empty file; edit with old: [] to insert.]" }], details: {} };
      }
      const selected = lines.slice(start, start + Math.min(args.limit ?? 2000, 2000));
      const output = truncateHead(selected.map((line) => `${hash(line)}│${line}`).join("\n"));
      if (output.firstLineExceedsLimit) {
        throw new Error(`Line ${start + 1} exceeds 50 KiB; use bash to inspect it.`);
      }
      const next = start + output.outputLines;
      const continuation = next < lines.length
        ? `\n\n[Showing lines ${start + 1}-${next} of ${lines.length}. Use offset=${next + 1} to continue.]`
        : "";
      return {
        content: [{ type: "text", text: output.content + continuation }],
        details: { truncation: output, nextOffset: next < lines.length ? next + 1 : undefined },
      };
    },
  });

  pi.registerTool({
    name: "edit",
    label: "edit",
    description:
      "Edit a file using content hashes from read. Each edit matches the consecutive sequence " +
      "before + old + after exactly once in the original file, then replaces only old with new. " +
      "Include every removed line's hash in old. Add adjacent before/after hashes to disambiguate " +
      "duplicate lines or hash collisions; context is preserved. old: [] inserts; new: [] deletes. An empty selector " +
      "is allowed only for an empty file. New lines are literal, without hash prefixes or embedded " +
      "CR/LF/NUL. All edits are validated before writing; ambiguous, stale, or overlapping targets fail. " +
      "Batch separate edits to the same file in one call. In results, + rows carry new hashes; - rows are removed lines.",
    promptSnippet: "Edit files by content hashes; supports batched replacements, insertions, and deletions",
    renderShell: "default",
    renderCall(args, theme) {
      return new Text(
        theme.fg("toolTitle", theme.bold("edit")) + " " + theme.fg("accent", args.path ?? "..."),
        0, 0,
      );
    },
    renderResult(result, { expanded }, theme, context) {
      const lines = result.content.filter((part) => part.type === "text")
        .map((part) => part.text).join("\n").split("\n");
      const visible = expanded ? lines : lines.slice(0, 10);
      let output = visible.map((line) => theme.fg(
        context.isError ? "error" : line.startsWith("+") ? "toolDiffAdded" :
          line.startsWith("-") ? "toolDiffRemoved" : "toolOutput",
        context.isError ? line : line.replace(/^([+-])(?:[A-Za-z]{4}|[0-9a-f]{16})│/, "$1"),
      )).join("\n");
      if (visible.length < lines.length) {
        output += theme.fg("muted", `\n... (${lines.length - visible.length} more lines, ${keyHint("app.tools.expand", "to expand")})`);
      }
      return new Text(output, 0, 0);
    },
    parameters: Type.Object({
      path: Type.String(),
      edits: Type.Array(Type.Object({
        before: Type.Optional(hashes),
        old: hashes,
        after: Type.Optional(hashes),
        new: Type.Array(Type.String({ pattern: "^[^\r\n\u0000]*$" })),
      }, { additionalProperties: false }), { minItems: 1 }),
    }, { additionalProperties: false }),
    async execute(_id, { path: inputPath, edits }, signal, _onUpdate, ctx) {
      const path = filePath(inputPath, ctx.cwd);
      return withFileMutationQueue(path, async () => {
        const { raw, bom, text, rows, lines } = await readText(path, signal);
        const anchors = lines.map(hash);
        const eol = text.match(/\r?\n/)?.[0] ?? "\n";
        const changes = edits.map((edit, index) => {
          const before = edit.before ?? [];
          const sequence = [...before, ...edit.old, ...(edit.after ?? [])];
          if (!sequence.length && lines.length) {
            throw new Error(`Edit ${index + 1}: supply old or adjacent context hashes.`);
          }
          if (edit.new.some((line) => /[\r\n\0]/.test(line))) {
            throw new Error(`Edit ${index + 1}: new must contain individual lines, without CR/LF/NUL.`);
          }
          let match = -1;
          for (let i = 0; i <= anchors.length - sequence.length; i++) {
            if (!sequence.every((anchor, j) => anchor === anchors[i + j])) continue;
            if (match !== -1) {
              throw new Error(`Edit ${index + 1}: ambiguous hashes; add adjacent before/after context.`);
            }
            match = i;
          }
          if (match === -1) {
            throw new Error(`Edit ${index + 1}: hashes not found (stale reference); read the file again.`);
          }
          const start = match + before.length;
          return { start, end: start + edit.old.length, replacement: edit.new };
        }).sort((a, b) => a.start - b.start);

        for (let i = 1; i < changes.length; i++) {
          if (changes[i].start < changes[i - 1].end || changes[i].start === changes[i - 1].start) {
            throw new Error("Overlapping edits (or insertions at the same position); merge them.");
          }
        }

        const updated: string[] = [];
        const diff: string[] = [];
        let cursor = 0;
        for (const { start, end, replacement } of changes) {
          for (let i = cursor; i < start; i++) updated.push(rows[i]);
          for (const [i, line] of replacement.entries()) {
            updated.push(start + i < end && line === lines[start + i] ? rows[start + i] : line + eol);
          }
          diff.push(`@@ original line ${start + 1} @@`);
          for (let i = start; i < end; i++) diff.push(`-${anchors[i]}│${lines[i]}`);
          for (const line of replacement) diff.push(`+${hash(line)}│${line}`);
          cursor = end;
        }
        for (let i = cursor; i < rows.length; i++) updated.push(rows[i]);
        // Inserting after an unterminated last line needs a separator, not a joined line.
        let result = updated.map((row, i) =>
          i < updated.length - 1 && !row.endsWith("\n") ? row + eol : row,
        ).join("");
        if (text && !text.endsWith("\n") && updated.at(-1) !== eol) {
          result = result.replace(/\r?\n$/, "");
        }
        const content = bom + result;
        if (content === raw) {
          return { content: [{ type: "text", text: "No changes made." }], details: {} };
        }
        signal?.throwIfAborted();
        // The shared queue also serializes this against Pi's built-in write tool.
        if (!(await readFile(path)).equals(Buffer.from(raw))) {
          throw new Error("File changed while preparing the edit; read it again.");
        }
        signal?.throwIfAborted();
        await writeFile(path, content, "utf8");
        const preview = truncateHead(diff.join("\n"));
        return {
          content: [{
            type: "text",
            text: `Applied ${changes.length} edit(s).\n\n` +
              preview.content + (preview.truncated ? "\n[Diff truncated; read for more context.]" : ""),
          }],
          details: {},
        };
      });
    },
  });
}