import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
import { Text } from "@earendil-works/pi-tui";
import { Type } from "typebox";

import type { ReadDocParams, DocgraphToolDetails } from "../types.js";
import { readFileSafe, parseMetadata, isInitialized, contentText } from "../utils.js";

export function registerDocgraphRead(pi: ExtensionAPI): void {
  pi.registerTool({
    name: "docgraph_read",
    label: "Docgraph Read",
    description:
      "Read a managed documentation file, returning its metadata block and body. Provides context for AI agents to determine relevance before reading the full file.",
    parameters: Type.Object({
      path: Type.String({
        description:
          "Relative path to the document (e.g. 'AGENTS.md', 'docs/SPEC.md')",
      }),
    }),

    async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
      const { path } = params as ReadDocParams;

      if (!isInitialized(ctx)) {
        return {
          content: [
            {
              type: "text",
              text: "Documentation not initialized. Run `docgraph_init` first.",
            },
          ],
          details: {
            action: "read",
            error: "not_initialized",
            state: { initialized: false, schemaVersion: 1 },
          } as DocgraphToolDetails,
        };
      }

      const raw = readFileSafe(path, ctx.cwd);
      if (raw === null) {
        return {
          content: [
            {
              type: "text",
              text: `Document not found: ${path}`,
            },
          ],
          details: {
            action: "read",
            error: "not_found",
            path,
            state: { initialized: true, schemaVersion: 1 },
          } as DocgraphToolDetails & { path: string },
        };
      }

      const metadata = parseMetadata(raw, path);

      // Separate metadata block from body
      const lines = raw.split("\n");
      let bodyStart = 0;
      let inMeta = false;
      for (let i = 0; i < lines.length; i++) {
        if (lines[i]!.startsWith("> **")) inMeta = true;
        if (inMeta && !lines[i]!.startsWith(">")) {
          bodyStart = i;
          break;
        }
      }
      const body = lines.slice(bodyStart).join("\n").trim();

      return {
        content: [
          {
            type: "text",
            text: [
              `## Metadata for \`${path}\``,
              `- **Purpose:** ${metadata.purpose}`,
              `- **Audience:** ${metadata.audience}`,
              `- **Last Updated:** ${metadata.lastUpdated}`,
              `- **Depends On:** ${metadata.dependsOn.join(", ") || "None"}`,
              `- **Referenced By:** ${metadata.referencedBy.join(", ") || "Unknown"}`,
              "",
              "## Body",
              body.slice(0, 4000), // Truncate very large docs
              body.length > 4000 ? "\n\n... (truncated)" : "",
            ].join("\n"),
          },
        ],
        details: {
          action: "read",
          path,
          metadata,
          bodyLength: body.length,
          state: { initialized: true, schemaVersion: 1 },
        } as DocgraphToolDetails & { path: string; metadata: typeof metadata; bodyLength: number },
      };
    },

    renderCall(args, theme) {
      return new Text(
        theme.fg("toolTitle", theme.bold("docgraph-read ")) +
          theme.fg("muted", args.path),
        0,
        0,
      );
    },

    renderResult(result, _opts, theme) {
      const text = contentText(result.content?.[0]);
      const firstLine = text.split("\n")[0] ?? "";
      return new Text(
        theme.fg("muted", firstLine),
        0,
        0,
      );
    },
  });
}