/**
 * pi-themes extension
 *
 * Bundles 10 popular color themes and provides a /theme command and
 * Ctrl+Shift+T shortcut to switch themes interactively.
 *
 * Themes included:
 *   catppuccin-mocha, catppuccin-latte, tokyo-night,
 *   gruvbox-dark, gruvbox-light, nord, dracula,
 *   solarized-dark, solarized-light, one-dark
 *
 * Usage:
 *   /theme                → open selector
 *   /theme tokyo-night    → switch directly by name
 *   Ctrl+Shift+T          → cycle through all themes
 */

import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";
import { DynamicBorder } from "@earendil-works/pi-coding-agent";
import { Container, Key, SelectList, Text, type AutocompleteItem, type SelectItem } from "@earendil-works/pi-tui";

export default function piThemesExtension(pi: ExtensionAPI) {
  // The name of the last theme activated through this extension.
  // We can't read the "current" theme back from the API, so we only track
  // changes that go through our own commands/shortcuts.
  let activeThemeName: string | undefined;

  // Cached list populated once on session_start for autocomplete.
  let cachedThemeNames: string[] = [];

  // ──────────────────────────────────────────────────────────
  // Helpers
  // ──────────────────────────────────────────────────────────

  function updateStatus(ctx: ExtensionContext) {
    if (activeThemeName) {
      ctx.ui.setStatus("pi-themes", ctx.ui.theme.fg("accent", `theme:${activeThemeName}`));
    } else {
      ctx.ui.setStatus("pi-themes", undefined);
    }
  }

  function applyTheme(name: string, ctx: ExtensionContext): boolean {
    const result = ctx.ui.setTheme(name);
    if (result.success) {
      activeThemeName = name;
      updateStatus(ctx);
      return true;
    }
    ctx.ui.notify(`Failed to apply theme "${name}": ${result.error}`, "error");
    return false;
  }

  // ──────────────────────────────────────────────────────────
  // Theme selector (custom SelectList UI)
  // ──────────────────────────────────────────────────────────

  async function showThemeSelector(ctx: ExtensionContext): Promise<void> {
    const themes = ctx.ui.getAllThemes();

    if (themes.length === 0) {
      ctx.ui.notify("No themes available.", "warning");
      return;
    }

    const items: SelectItem[] = themes.map((t) => ({
      value: t.name,
      label: t.name === activeThemeName ? `${t.name} (active)` : t.name,
      description: t.path ? shortenPath(t.path) : "built-in",
    }));

    const selected = await ctx.ui.custom<string | null>((tui, theme, _kb, done) => {
      const container = new Container();
      container.addChild(new DynamicBorder((str) => theme.fg("accent", str)));
      container.addChild(new Text(theme.fg("accent", theme.bold(" Select Theme"))));

      const selectList = new SelectList(items, Math.min(items.length, 14), {
        selectedPrefix: (text) => theme.fg("accent", text),
        selectedText:   (text) => theme.fg("accent", text),
        description:    (text) => theme.fg("dim", text),
        scrollInfo:     (text) => theme.fg("dim", text),
        noMatch:        (text) => theme.fg("warning", text),
      });

      selectList.onSelect = (item) => done(item.value);
      selectList.onCancel = () => done(null);

      container.addChild(selectList);
      container.addChild(
        new Text(theme.fg("dim", " ↑↓ navigate  •  / filter  •  enter select  •  esc cancel"))
      );
      container.addChild(new DynamicBorder((str) => theme.fg("accent", str)));

      return {
        render(width: number) {
          return container.render(width);
        },
        invalidate() {
          container.invalidate();
        },
        handleInput(data: string) {
          selectList.handleInput(data);
          tui.requestRender();
        },
      };
    });

    if (!selected) return;

    if (applyTheme(selected, ctx)) {
      ctx.ui.notify(`Theme "${selected}" activated`, "info");
    }
  }

  // ──────────────────────────────────────────────────────────
  // Cycle through all available themes
  // ──────────────────────────────────────────────────────────

  function cycleTheme(ctx: ExtensionContext): void {
    const themes = ctx.ui.getAllThemes();
    if (themes.length === 0) return;

    const names = themes.map((t) => t.name);
    const currentIdx = activeThemeName ? names.indexOf(activeThemeName) : -1;
    const nextName = names[(currentIdx + 1) % names.length];

    if (applyTheme(nextName, ctx)) {
      ctx.ui.notify(`Theme: ${nextName}`, "info");
    }
  }

  // ──────────────────────────────────────────────────────────
  // Registration
  // ──────────────────────────────────────────────────────────

  pi.registerShortcut(Key.ctrlShift("t"), {
    description: "Cycle themes (pi-themes)",
    handler: async (ctx) => {
      cycleTheme(ctx);
    },
  });

  pi.registerCommand("theme", {
    description: "Select or switch pi theme  •  /theme <name> or Ctrl+Shift+T to cycle",

    getArgumentCompletions(prefix: string): AutocompleteItem[] | null {
      const filtered = cachedThemeNames.filter((n) => n.startsWith(prefix));
      if (filtered.length === 0) return null;
      return filtered.map((n) => ({ value: n, label: n }));
    },

    handler: async (args, ctx) => {
      const name = args?.trim();

      if (name) {
        // Direct switch by name
        const allNames = ctx.ui.getAllThemes().map((t) => t.name);
        if (!allNames.includes(name)) {
          ctx.ui.notify(
            `Unknown theme "${name}". Available: ${allNames.join(", ")}`,
            "error"
          );
          return;
        }
        if (applyTheme(name, ctx)) {
          ctx.ui.notify(`Theme "${name}" activated`, "info");
        }
        return;
      }

      // No arg → interactive selector
      await showThemeSelector(ctx);
    },
  });

  // ──────────────────────────────────────────────────────────
  // Session lifecycle
  // ──────────────────────────────────────────────────────────

  pi.on("session_start", async (_event, ctx) => {
    cachedThemeNames = ctx.ui.getAllThemes().map((t) => t.name);
    updateStatus(ctx);
  });
}

// ──────────────────────────────────────────────────────────
// Utilities
// ──────────────────────────────────────────────────────────

/** Abbreviate long absolute paths for the selector description column. */
function shortenPath(p: string): string {
  const home = process.env.HOME ?? "";
  if (home && p.startsWith(home)) {
    return "~" + p.slice(home.length);
  }
  return p;
}