import { useCallback, useMemo, type ReactNode } from "react";
import { useTheme } from "next-themes";
import type { FileDiffOptions, SelectedLineRange, FileDiffMetadata } from "@pierre/diffs";
import { IconPlus } from "@tabler/icons-react";
import { FONT } from "@/lib/theme/colors";
import { useGlobalViewMode } from "@/hooks/use-global-view-mode";
import { useDiffHeaderToolbar } from "./diff-header-toolbar";
import type { AnnotationMetadata } from "./use-diff-annotation-renderer";

/** CSS overrides for the Pierre diff viewer, injected via unsafeCSS. */
const DIFF_UNSAFE_CSS = `
  :host {
    --diffs-bg: var(--background) !important;
    --diffs-bg-context: var(--background) !important;
    --diffs-bg-buffer: var(--card) !important;
    --diffs-bg-separator: var(--card) !important;
    --diffs-bg-hover: var(--muted) !important;
    --diffs-fg: var(--foreground) !important;
    --diffs-fg-number: var(--muted-foreground) !important;
    --diffs-addition-color-override: rgb(var(--git-addition)) !important;
    --diffs-deletion-color-override: rgb(var(--git-deletion)) !important;
    --diffs-bg-addition: rgb(var(--git-addition) / 0.1) !important;
    --diffs-bg-deletion: rgb(var(--git-deletion) / 0.1) !important;
    --diffs-bg-addition-number: rgb(var(--git-addition) / 0.15) !important;
    --diffs-bg-deletion-number: rgb(var(--git-deletion) / 0.15) !important;
    --diffs-bg-addition-emphasis: rgb(var(--git-addition) / 0.3) !important;
    --diffs-bg-deletion-emphasis: rgb(var(--git-deletion) / 0.3) !important;
    --diffs-line-height: 24px !important;
    --diffs-font-size: ${FONT.size}px !important;
    --diffs-font-family: ${FONT.mono} !important;
    --diffs-gap-fallback: 0;
    font-size: ${FONT.size}px !important;
    font-family: ${FONT.mono} !important;
  }
  [data-line] {
    min-height: 24px !important;
    line-height: 24px !important;
  }
  [data-separator='metadata'],
  [data-separator]:empty {
    height: 24px !important;
    background-image: repeating-linear-gradient(-45deg, transparent, transparent calc(3px * 1.414), var(--diffs-bg-buffer) calc(3px * 1.414), var(--diffs-bg-buffer) calc(4px * 1.414));
    background-color: transparent !important;
    border-top: 1px solid var(--diffs-bg-separator) !important;
    border-bottom: 1px solid var(--diffs-bg-separator) !important;
  }
  [data-change-icon] {
    width: 12px !important;
    height: 12px !important;
  }
  [data-diffs-header] {
    padding-inline: 12px !important;
    background: var(--card) !important;
  }
  [data-header-content] {
    display: flex !important;
    align-items: center !important;
    gap: 6px !important;
    min-width: 0 !important;
  }
  [data-title],
  [data-prev-name] {
    min-width: 0 !important;
  }
  [data-title] bdi,
  [data-prev-name] bdi {
    display: block !important;
    overflow: hidden !important;
    text-overflow: ellipsis !important;
    white-space: nowrap !important;
  }
  /* Vertically center the "Add comment" hover button in the line gutter.
     Pierre 1.1.22 declares the slot wrapper as display:flex with top:0/bottom:0
     but no align-items, so our fixed-size button pins to the top of the line
     cell instead of centering on the line number. */
  [data-gutter-utility-slot] {
    align-items: center !important;
  }
`;

type UseDiffOptionsArgs = {
  filePath: string;
  diff?: string;
  enableComments: boolean;
  showHeader: boolean;
  wordWrap: boolean;
  setWordWrap: (fn: (v: boolean) => boolean) => void;
  handleLineSelectionEnd: (range: SelectedLineRange | null) => void;
  onLineEnter: (props: { lineType?: string; lineNumber?: number; annotationSide?: string }) => void;
  onLineLeave: () => void;
  onOpenFile?: (filePath: string, repo?: string) => void;
  onPreviewMarkdown?: (filePath: string) => void;
  onRevert?: (filePath: string) => void;
  /** Multi-repo subpath (repository_name) so Edit opens under the right repo. */
  repo?: string;
  /** Enable diff expansion (requires full deletionLines/additionLines in metadata) */
  enableExpansion?: boolean;
  /** Number of lines to expand per click (default: 20) */
  expansionLineCount?: number;
  /** When true, show all lines (no separators) */
  expandUnchanged?: boolean;
  /** Toggle callback for expand-all button */
  onToggleExpandUnchanged?: () => void;
};

type UseDiffOptionsResult = {
  globalViewMode: string;
  options: FileDiffOptions<AnnotationMetadata>;
  renderHeaderMetadata: ((fileDiff: FileDiffMetadata) => ReactNode) | undefined;
  renderHoverUtility: () => ReactNode;
};

export function useDiffOptions(args: UseDiffOptionsArgs): UseDiffOptionsResult {
  const {
    filePath,
    diff,
    enableComments,
    showHeader,
    wordWrap,
    setWordWrap,
    handleLineSelectionEnd,
    onLineEnter,
    onLineLeave,
    onOpenFile,
    onPreviewMarkdown,
    onRevert,
    repo,
    enableExpansion = false,
    expansionLineCount = 20,
    expandUnchanged,
    onToggleExpandUnchanged,
  } = args;

  const { resolvedTheme } = useTheme();
  const [globalViewMode, setGlobalViewMode] = useGlobalViewMode();

  const toggleViewMode = useCallback(
    () => setGlobalViewMode(globalViewMode === "split" ? "unified" : "split"),
    [globalViewMode, setGlobalViewMode],
  );

  const toggleWordWrap = useCallback(() => setWordWrap((v: boolean) => !v), [setWordWrap]);

  const renderHeaderMetadata = useDiffHeaderToolbar({
    filePath,
    diff,
    wordWrap,
    onToggleWordWrap: toggleWordWrap,
    viewMode: globalViewMode,
    onToggleViewMode: toggleViewMode,
    onOpenFile,
    onPreviewMarkdown,
    onRevert,
    repo,
    expandUnchanged,
    onToggleExpandUnchanged,
  });

  const renderHoverUtility = useCallback((): ReactNode => {
    if (!enableComments) return null;
    return (
      <div
        // Negative margin mirrors pierre's default [data-utility-button] trick:
        // the slot wrapper is right:0 of the line-number cell, so without this
        // the button sits inside the cell and overlaps the number. Pulling
        // right by (1ch - 1lh) extrudes the button past the gutter's right
        // edge into the code area, same as pierre's built-in button does.
        style={{ marginRight: "calc(1ch - 1lh)" }}
        className="flex h-5 w-5 cursor-pointer items-center justify-center rounded border border-border bg-background text-muted-foreground hover:bg-accent hover:text-foreground"
        title="Add comment"
      >
        <IconPlus className="h-3 w-3" />
      </div>
    );
  }, [enableComments]);

  const options = useMemo<FileDiffOptions<AnnotationMetadata>>(() => {
    return {
      diffStyle: globalViewMode,
      themeType: resolvedTheme === "dark" ? "dark" : "light",
      enableLineSelection: enableComments,
      // "line-info" shows expand buttons when full deletionLines/additionLines are on metadata;
      // "simple" is a plain divider without expand controls.
      hunkSeparators: enableExpansion ? "line-info" : "simple",
      enableHoverUtility: enableComments,
      diffIndicators: "none",
      onLineSelectionEnd: handleLineSelectionEnd,
      onLineEnter,
      onLineLeave,
      disableFileHeader: !showHeader,
      overflow: wordWrap ? "wrap" : "scroll",
      unsafeCSS: DIFF_UNSAFE_CSS,
      expansionLineCount,
      expandUnchanged,
    };
  }, [
    globalViewMode,
    resolvedTheme,
    enableComments,
    showHeader,
    handleLineSelectionEnd,
    wordWrap,
    onLineEnter,
    onLineLeave,
    enableExpansion,
    expansionLineCount,
    expandUnchanged,
  ]);

  return {
    globalViewMode,
    options,
    renderHeaderMetadata: showHeader ? renderHeaderMetadata : undefined,
    renderHoverUtility,
  };
}