/**
 * oh-pi Compact Header — table-style startup info with dynamic column widths
 */
import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
import { VERSION } from "@mariozechner/pi-coding-agent";
import { truncateToWidth, visibleWidth } from "@mariozechner/pi-tui";

export default function (pi: ExtensionAPI) {
  pi.on("session_start", async (_event, ctx) => {
    if (!ctx.hasUI) return;

    ctx.ui.setHeader((_tui, theme) => ({
      render(width: number): string[] {
        const d = (s: string) => theme.fg("dim", s);
        const a = (s: string) => theme.fg("accent", s);

        const cmds = pi.getCommands();
        const prompts = cmds.filter(c => c.source === "prompt").map(c => `/${c.name}`).join("  ");
        const skills = cmds.filter(c => c.source === "skill").map(c => c.name).join("  ");
        const model = ctx.model ? `${ctx.model.id}` : "no model";
        const thinking = pi.getThinkingLevel();
        const provider = ctx.model?.provider ?? "";

        const pad = (s: string, w: number) => s + " ".repeat(Math.max(0, w - visibleWidth(s)));
        const t = (s: string) => truncateToWidth(s, width);
        const sep = d(" │ ");

        // Right two columns are fixed width
        const rCol = [
          [d("esc"), a("interrupt"),   d("S-tab"), a("thinking")],
          [d("^C"),  a("clear/exit"),  d("^O"),    a("expand")],
          [d("^P"),  a("model"),       d("^G"),    a("editor")],
          [d("/"),   a("commands"),    d("^V"),    a("paste")],
          [d("!"),   a("bash"),        d(""),      a("")],
        ];
        const k1w = 6, v1w = 13, k2w = 6, v2w = 9;
        const rightW = k1w + v1w + 3 + k2w + v2w + 3; // 3 for each sep

        // Left column gets remaining space
        const leftW = Math.max(20, width - rightW);
        const lk = 9; // label width

        const lCol = [
          [d("version"), a(`v${VERSION}  ${provider}`)],
          [d("model"),   a(model)],
          [d("think"),   a(thinking)],
          [d(""),        d("")],
          [d(""),        d("")],
        ];

        const lines: string[] = [""];
        for (let i = 0; i < 5; i++) {
          const [lk0, lv0] = lCol[i];
          const [rk0, rv0, rk1, rv1] = rCol[i];
          const left = truncateToWidth(pad(lk0, lk) + lv0, leftW);
          const right = pad(rk0, k1w) + pad(rv0, v1w) + sep + pad(rk1, k2w) + rv1;
          lines.push(t(pad(left, leftW) + sep + right));
        }

        if (prompts) lines.push(t(`${pad(d("prompts"), lk)}${a(prompts)}`));
        if (skills) lines.push(t(`${pad(d("skills"), lk)}${a(skills)}`));
        lines.push(d("─".repeat(width)));

        return lines;
      },
      invalidate() {},
    }));
  });
}