/**
 * usePretextRowHeights
 *
 * Pre-computes row heights using pretext text measurement.
 * For each row, measures each cell's height at the given column width,
 * then takes the maximum + padding as the row height.
 */
import { computed, type Ref } from "vue";
import { measureTextHeight } from "./measureText";
import type { ListTableColumn } from "./types";
import { toRefs } from "@vueuse/core";

const DEFAULT_FONT = "14px Inter, sans-serif";
const DEFAULT_LINE_HEIGHT = 20;
const DEFAULT_ROW_PADDING = 5;
const CELL_VERTICAL_PADDING = 12; // top + bottom per cell

export interface RowHeightEntry {
  height: number;
  isCustomRenderer: boolean;
}

export function resolveRowHeights<T>(
  data: Ref<T[]>,
  columns: Ref<ListTableColumn<T>[]>,
  columnWidths: Ref<number[]>,
  lineMaxWidth: number,
  formatCellValue: (row: T, col: ListTableColumn<T>) => string,
  options?: {
    font?: string;
    lineHeight?: number;
    rowPadding?: number;
    fixedRowHeight?: number;
    debug?: boolean;
  }
) {
  const font = options?.font ?? DEFAULT_FONT;
  const lineHeight = options?.lineHeight ?? DEFAULT_LINE_HEIGHT;
  const rowPadding = options?.rowPadding ?? DEFAULT_ROW_PADDING;

  const { rowHeights, cellHeights } = toRefs(
    computed(() => {
      if (!data.value.length || !columns.value.length || !columnWidths.value.length) {
        return { rowHeights: [], cellHeights: [] };
      }

      const rowHeights: number[] = [];
      const cellHeights: Array<RowHeightEntry | null>[] | undefined = options?.debug ? [] : undefined;

      for (const row of data.value) {
        let maxCellHeight = lineHeight; // minimum 1 line
        let rowCellHeights: Array<RowHeightEntry | null> = [];

        for (let i = 0; i < columns.value.length; i++) {
          const col = columns.value[i];
          // Use flex basis width for height calculation as an approximation
          // of actual column width (CSS flex layout determines actual width)
          const colWidth = columnWidths.value[i] ?? 120;

          // Check if custom renderer exists (we can't measure these with pretext)
          const isCustomRenderer = !!(col.cellRenderer || col.slot);
          let rowHeightEntry: RowHeightEntry;

          if (options?.fixedRowHeight) {
            rowHeightEntry = {
              height: options.fixedRowHeight,
              isCustomRenderer,
            };
          } else if (isCustomRenderer) {
            rowHeightEntry = {
              height: 42,
              isCustomRenderer,
            };
          } else {
            try {
              const cellText = formatCellValue(row, col);
              if (!cellText) throw "Invalid Cell Text";

              // Calculate available width for text (excluding cell padding)
              const availableWidth = Math.min(colWidth - CELL_VERTICAL_PADDING * 2, col.maxTextWidth ?? lineMaxWidth);
              if (availableWidth <= 0) throw "Invalid Column Width";

              rowHeightEntry = {
                height: measureTextHeight(cellText, font, availableWidth, lineHeight),
                isCustomRenderer,
              };
            } catch {
              // Fallback: assume single line
              rowHeightEntry = {
                height: 42,
                isCustomRenderer,
              };
            }
          }

          maxCellHeight = Math.max(maxCellHeight, rowHeightEntry?.height ?? 0);
          if (options?.debug) {
            rowCellHeights.push(rowHeightEntry);
          }
        }

        const rowHeight = maxCellHeight + rowPadding * 2;
        rowHeights.push(rowHeight);
        cellHeights?.push(rowCellHeights);
      }

      return {
        rowHeights,
        cellHeights,
      };
    })
  );

  // Total height (sum of all row heights) - useful for virtualizer
  const totalHeight = computed(() => rowHeights.value.reduce((sum, height) => sum + height, 0));

  return {
    rowHeights,
    totalHeight,
    cellHeights,
  };
}