/**
 * Mouse-click support via SGR mouse reporting.
 *
 * SGR mode (`CSI ? 1006 h`) is the modern, well-supported encoding —
 * iTerm2, kitty, Alacritty, WezTerm, modern Windows Terminal all
 * speak it. Format on press: `ESC [ < button ; col ; row M`; on
 * release the trailing M becomes m.
 *
 * Buttons in SGR mode:
 *   0 = left, 1 = middle, 2 = right
 *   64 = wheel up, 65 = wheel down
 *   modifiers (shift/alt/ctrl) get OR'd into the button code (4/8/16)
 *
 * `CSI ? 1000 h` enables button-event reporting (presses + releases,
 * no motion). We don't need motion or any-event mode for click-to-
 * focus.
 */

const ESC = '\x1b';

export const MOUSE_ON = `${ESC}[?1000h${ESC}[?1006h`;
export const MOUSE_OFF = `${ESC}[?1000l${ESC}[?1006l`;

export interface MouseEvent {
  button: number;
  /** 0-based terminal column. SGR reports 1-based; we normalize. */
  col: number;
  /** 0-based terminal row. */
  row: number;
  pressed: boolean;
}

/**
 * Match an SGR mouse sequence in a chunk of input. Ink's `useInput`
 * sees mouse events as `key.escape: true` + an `input` like
 * `[<0;5;3M`, so we accept both that form (Ink-relayed) and the raw
 * form including the leading ESC + CSI. Built from a string at
 * runtime so the `\x1b` control byte doesn't trip biome's "control
 * character in regex" lint.
 */
const SGR_PATTERN = new RegExp(`^(?:${ESC}\\[|\\[)<(\\d+);(\\d+);(\\d+)([Mm])`);

export function parseMouseEvent(input: string): MouseEvent | null {
  const match = input.match(SGR_PATTERN);
  if (!match) return null;
  return {
    button: Number.parseInt(match[1], 10),
    // SGR coordinates are 1-based; our layout math is 0-based.
    col: Number.parseInt(match[2], 10) - 1,
    row: Number.parseInt(match[3], 10) - 1,
    pressed: match[4] === 'M',
  };
}

export interface ClickRegions {
  /** Width and height of the body (everything above the keybar). */
  bodyHeight: number;
  leftColWidth: number;
  /** rightColWidth is implied by total columns; not needed for hit-testing. */
  summaryHeight: number;
  categoriesHeight: number;
  // findingsHeight is the remainder of the left column.
  detailHeight: number;
  // commandLogHeight is the remainder of the right column.
}

export type PaneId = 'summary' | 'categories' | 'findings' | 'detail' | 'log';

export interface PaneHit {
  pane: PaneId;
  /**
   * 0-based row offset relative to the pane's top edge (border
   * inclusive). Useful for translating a click into a list index in
   * scrollable panes.
   */
  rowInPane: number;
}

/**
 * Hit-test a click against the pane layout. Returns the pane the
 * click landed in (with the row offset within that pane), or null
 * if the click is outside the body (e.g. keybar row).
 */
export function paneAt(col: number, row: number, regions: ClickRegions): PaneHit | null {
  if (row < 0 || row >= regions.bodyHeight) return null;
  if (col < 0) return null;

  if (col < regions.leftColWidth) {
    if (row < regions.summaryHeight) {
      return { pane: 'summary', rowInPane: row };
    }
    if (row < regions.summaryHeight + regions.categoriesHeight) {
      return { pane: 'categories', rowInPane: row - regions.summaryHeight };
    }
    return {
      pane: 'findings',
      rowInPane: row - regions.summaryHeight - regions.categoriesHeight,
    };
  }

  // Right column.
  if (row < regions.detailHeight) {
    return { pane: 'detail', rowInPane: row };
  }
  return { pane: 'log', rowInPane: row - regions.detailHeight };
}

/**
 * Each pane's "chrome" — non-content rows above the first list item.
 * Categories: top border (1) + title (1) + marginTop spacer (1) = 3.
 * Findings:   same. (Bottom border doesn't matter; we only care
 * about the top offset.)
 */
export const LIST_PANE_CHROME = 3;