/**
 * mermaidDiff — F7.1 (#22) dispatcher. Detects a mermaid diagram's type and
 * routes a baseline→current diff to the matching pure differ, which re-emits the
 * CURRENT diagram source augmented with mermaid styling directives (INV-29). Any
 * unsupported type or parser surprise degrades to the v1 whole-block badge
 * (INV-30) — this function never throws. vscode-free, DOM-free, deterministic.
 */
import { diffFlowchart } from "./mermaidFlowchartDiff";
import { diffSequence } from "./mermaidSequenceDiff";

/** Theme-neutral colors baked into emitted mermaid source (source can't read CSS vars). */
export const CW_COLORS = {
  added: "#2ea043",
  changed: "#d29922",
  removed: "#808080",
} as const;

export type DiagramType = "flowchart" | "sequence" | "other";

export interface MermaidDiffAugmented {
  kind: "augmented";
  source: string;
}
export interface MermaidDiffFallback {
  kind: "fallback";
}
export type MermaidDiffResult = MermaidDiffAugmented | MermaidDiffFallback;

export function detectDiagramType(source: string): DiagramType {
  for (const line of source.split(/\r?\n/)) {
    const t = line.trim();
    if (t === "" || t.startsWith("%%")) continue;
    if (/^(flowchart|graph)\b/.test(t)) return "flowchart";
    if (/^sequenceDiagram\b/.test(t)) return "sequence";
    return "other";
  }
  return "other";
}

export function diffMermaid(beforeSrc: string, currentSrc: string): MermaidDiffResult {
  const type = detectDiagramType(currentSrc);
  try {
    if (type === "flowchart") return { kind: "augmented", source: diffFlowchart(beforeSrc, currentSrc) };
    if (type === "sequence") return { kind: "augmented", source: diffSequence(beforeSrc, currentSrc) };
  } catch {
    return { kind: "fallback" };
  }
  return { kind: "fallback" };
}