import { createFilter, type Plugin } from "vite";

type LimitLineOverride = {
  files: string;
  maxReactFCLines: number | null;
  maxFileLines: number | null;
};

type LimitLineOptions = {
  maxReactFCLines: number;
  maxFileLines: number;
  include: RegExp;
  exclude: RegExp | null;
  overrides: Array<LimitLineOverride>;
};

const DEFAULT_OPTIONS: LimitLineOptions = {
  maxReactFCLines: 300,
  maxFileLines: 600,
  include: /\.[tj]sx$/,
  exclude: null,
  overrides: [],
};

type ResolvedLimits = {
  maxReactFCLines: number | null;
  maxFileLines: number | null;
};

type ComponentInfo = {
  name: string;
  startLine: number;
  lineCount: number;
};

const PASCAL_CASE = /^[A-Z][A-Za-z0-9]*$/;

type AstNode = {
  type: string;
  start: number;
  end: number;
  id: { name: string } | null;
  init: AstNode | null;
  declaration: AstNode | null;
  declarations: Array<{ id: { name: string }; init: AstNode | null }>;
  callee: { name: string } | null;
  arguments: Array<AstNode>;
  body: Array<AstNode>;
  [key: string]: unknown;
};

function lineAt(code: string, offset: number): number {
  let line = 1;
  for (let i = 0; i < offset && i < code.length; i++) {
    if (code[i] === "\n") line++;
  }
  return line;
}

function lineSpan(code: string, start: number, end: number): { startLine: number; lineCount: number } {
  const startLine = lineAt(code, start);
  const endLine = lineAt(code, end);
  return { startLine, lineCount: endLine - startLine + 1 };
}

function extractComponents(ast: AstNode, code: string): Array<ComponentInfo> {
  const results: Array<ComponentInfo> = [];

  for (const node of ast.body ?? []) {
    if (node.type === "FunctionDeclaration" && node.id && PASCAL_CASE.test(node.id.name)) {
      const span = lineSpan(code, node.start, node.end);
      results.push({ name: node.id.name, ...span });
      continue;
    }

    if (node.type === "ExportNamedDeclaration" && node.declaration) {
      const decl = node.declaration;

      if (decl.type === "FunctionDeclaration" && decl.id && PASCAL_CASE.test(decl.id.name)) {
        const span = lineSpan(code, node.start, node.end);
        results.push({ name: decl.id.name, ...span });
        continue;
      }

      if (decl.type === "VariableDeclaration") {
        collectFromVarDeclaration(decl, code, results);
        continue;
      }
    }

    if (node.type === "VariableDeclaration") {
      collectFromVarDeclaration(node, code, results);
    }
  }

  return results;
}

function collectFromVarDeclaration(node: AstNode, code: string, results: Array<ComponentInfo>): void {
  for (const declarator of node.declarations ?? []) {
    if (!declarator.id || !PASCAL_CASE.test(declarator.id.name) || !declarator.init) continue;

    const init = declarator.init;

    if (isFunctionLike(init)) {
      const span = lineSpan(code, node.start, node.end);
      results.push({ name: declarator.id.name, ...span });
    } else if (isWrapperCall(init) && init.arguments.length > 0 && isFunctionLike(init.arguments[0])) {
      const span = lineSpan(code, node.start, node.end);
      results.push({ name: declarator.id.name, ...span });
    }
  }
}

function isFunctionLike(node: AstNode): boolean {
  return node.type === "ArrowFunctionExpression" || node.type === "FunctionExpression";
}

const WRAPPER_NAMES = new Set(["memo", "forwardRef", "lazy"]);

function isWrapperCall(node: AstNode): boolean {
  return node.type === "CallExpression" && node.callee !== null && node.callee.name !== undefined && WRAPPER_NAMES.has(node.callee.name);
}

function createLimitResolver(options: LimitLineOptions): (id: string) => ResolvedLimits {
  const matchers = options.overrides.map((override) => ({
    match: createFilter(override.files),
    maxReactFCLines: override.maxReactFCLines,
    maxFileLines: override.maxFileLines,
  }));

  return (id: string): ResolvedLimits => {
    let maxReactFCLines: number | null = options.maxReactFCLines;
    let maxFileLines: number | null = options.maxFileLines;

    for (const matcher of matchers) {
      if (matcher.match(id)) {
        maxReactFCLines = matcher.maxReactFCLines;
        maxFileLines = matcher.maxFileLines;
      }
    }

    return { maxReactFCLines, maxFileLines };
  };
}

function shouldProcess(id: string, options: LimitLineOptions): boolean {
  return options.include.test(id) && !id.includes("node_modules") && (options.exclude === null || !options.exclude.test(id));
}

function viteLimitLinePlugin(
  userOptions: Partial<LimitLineOptions> = {},
): Array<Plugin> {
  const options: LimitLineOptions = { ...DEFAULT_OPTIONS, ...userOptions, overrides: userOptions.overrides ?? [] };
  const resolve = createLimitResolver(options);

  return [
    {
      name: "vite-plugin-file-line-limit",
      enforce: "pre",

      transform(code, id) {
        if (!shouldProcess(id, options)) return null;

        const limits = resolve(id);
        if (limits.maxFileLines === null) return null;

        const totalLines = code.split("\n").length;
        if (totalLines > limits.maxFileLines) {
          this.error(
            [
              `[vite-limit-line] File too long: ${totalLines} lines (limit: ${limits.maxFileLines})`,
              `  file: ${id}`,
              "",
              "How to fix:",
              "  Split this file into smaller modules — extract related types, helpers,",
              "  or sub-components into separate files and re-export from an index.ts.",
            ].join("\n"),
          );
        }

        return null;
      },
    },
    {
      name: "vite-plugin-react-fc-line-limit",

      transform(code, id) {
        if (!shouldProcess(id, options)) return null;

        const limits = resolve(id);
        if (limits.maxReactFCLines === null) return null;

        const ast = this.parse(code) as unknown as AstNode;
        const components = extractComponents(ast, code);
        const violations = components.filter((c) => c.lineCount > (limits.maxReactFCLines as number));

        if (violations.length > 0) {
          const details = violations
            .map(
              (v) =>
                `  ${v.name} (line ${v.startLine}): ${v.lineCount} lines (limit: ${limits.maxReactFCLines})`,
            )
            .join("\n");

          this.error(
            [
              `[vite-limit-line] React component too long in ${id}:`,
              details,
              "",
              "How to fix:",
              "  Break each oversized component into smaller ones. Extract reusable",
              "  sections into child components, move complex logic into custom hooks,",
              "  and keep each component focused on a single responsibility.",
            ].join("\n"),
          );
        }

        return null;
      },
    },
  ];
}

export { viteLimitLinePlugin };
export type { LimitLineOptions, LimitLineOverride };