import { execFileSync } from "node:child_process";
import path from "node:path";
import ts from "typescript";
import type { CanonicalSymbol, ProgramContext, SymbolKind } from "./types.js";

function assert(condition: unknown, message: string): asserts condition {
  if (!condition) {
    throw new Error(message);
  }
}

export function normalizePath(filePath: string): string {
  return filePath.split(path.sep).join(path.posix.sep);
}

export function createProgramContext(
  repoRoot: string,
  tsconfigName = "tsconfig.json",
): ProgramContext {
  const configPath = ts.findConfigFile(
    repoRoot,
    (candidate) => ts.sys.fileExists(candidate),
    tsconfigName,
  );
  assert(configPath, `Could not find ${tsconfigName}`);
  const configFile = ts.readConfigFile(configPath, (candidate) => ts.sys.readFile(candidate));
  if (configFile.error) {
    throw new Error(ts.flattenDiagnosticMessageText(configFile.error.messageText, "\n"));
  }
  const parsed = ts.parseJsonConfigFileContent(configFile.config, ts.sys, repoRoot);
  const program = ts.createProgram(parsed.fileNames, parsed.options);
  return {
    repoRoot,
    tsconfigPath: normalizePath(path.relative(repoRoot, configPath)),
    program,
    checker: program.getTypeChecker(),
    normalizePath,
    relativeToRepo(filePath: string) {
      return normalizePath(path.relative(repoRoot, filePath));
    },
  };
}

export function comparableSymbol(
  checker: ts.TypeChecker,
  symbol: ts.Symbol | undefined,
): ts.Symbol | undefined {
  if (!symbol) {
    return undefined;
  }
  return symbol.flags & ts.SymbolFlags.Alias ? checker.getAliasedSymbol(symbol) : symbol;
}

function symbolKind(symbol: ts.Symbol, declaration: ts.Declaration | undefined): SymbolKind {
  if (declaration) {
    switch (declaration.kind) {
      case ts.SyntaxKind.FunctionDeclaration:
        return "function";
      case ts.SyntaxKind.ClassDeclaration:
        return "class";
      case ts.SyntaxKind.InterfaceDeclaration:
        return "interface";
      case ts.SyntaxKind.TypeAliasDeclaration:
        return "type";
      case ts.SyntaxKind.EnumDeclaration:
        return "enum";
      case ts.SyntaxKind.VariableDeclaration:
        return "variable";
      default:
        break;
    }
  }
  if (symbol.flags & ts.SymbolFlags.Function) {
    return "function";
  }
  if (symbol.flags & ts.SymbolFlags.Class) {
    return "class";
  }
  if (symbol.flags & ts.SymbolFlags.Interface) {
    return "interface";
  }
  if (symbol.flags & ts.SymbolFlags.TypeAlias) {
    return "type";
  }
  if (symbol.flags & ts.SymbolFlags.Enum) {
    return "enum";
  }
  if (symbol.flags & ts.SymbolFlags.Variable) {
    return "variable";
  }
  return "unknown";
}

export function canonicalSymbolInfo(context: ProgramContext, symbol: ts.Symbol): CanonicalSymbol {
  const resolved = comparableSymbol(context.checker, symbol) ?? symbol;
  const declaration =
    resolved.getDeclarations()?.find((candidate) => candidate.kind !== ts.SyntaxKind.SourceFile) ??
    symbol.getDeclarations()?.find((candidate) => candidate.kind !== ts.SyntaxKind.SourceFile);
  assert(declaration, `Missing declaration for symbol ${symbol.getName()}`);
  const sourceFile = declaration.getSourceFile();
  const declarationPath = context.relativeToRepo(sourceFile.fileName);
  const declarationLine = sourceFile.getLineAndCharacterOfPosition(declaration.getStart()).line + 1;
  return {
    canonicalKey: `${declarationPath}:${declarationLine}:${resolved.getName()}`,
    declarationPath,
    declarationLine,
    kind: symbolKind(resolved, declaration),
    aliasName: symbol.getName() !== resolved.getName() ? symbol.getName() : undefined,
  };
}

export function countIdentifierUsages(
  context: ProgramContext,
  sourceFile: ts.SourceFile,
  importedSymbol: ts.Symbol,
  localName: string,
): number {
  const targetSymbol = comparableSymbol(context.checker, importedSymbol);
  let count = 0;
  const visit = (node: ts.Node) => {
    if (ts.isIdentifier(node) && node.text === localName) {
      const symbol = comparableSymbol(context.checker, context.checker.getSymbolAtLocation(node));
      if (
        symbol === targetSymbol &&
        !ts.isImportClause(node.parent) &&
        !ts.isImportSpecifier(node.parent)
      ) {
        count += 1;
      }
    }
    ts.forEachChild(node, visit);
  };
  ts.forEachChild(sourceFile, visit);
  return count;
}

export function countNamespacePropertyUsages(
  context: ProgramContext,
  sourceFile: ts.SourceFile,
  namespaceSymbol: ts.Symbol,
  exportedName: string,
): number {
  const targetSymbol = comparableSymbol(context.checker, namespaceSymbol);
  let count = 0;
  const visit = (node: ts.Node) => {
    if (
      ts.isPropertyAccessExpression(node) &&
      ts.isIdentifier(node.expression) &&
      node.name.text === exportedName
    ) {
      const symbol = comparableSymbol(
        context.checker,
        context.checker.getSymbolAtLocation(node.expression),
      );
      if (symbol === targetSymbol) {
        count += 1;
      }
    }
    ts.forEachChild(node, visit);
  };
  ts.forEachChild(sourceFile, visit);
  return count;
}

export function getRepoRevision(repoRoot: string): string | null {
  try {
    return execFileSync("git", ["rev-parse", "HEAD"], {
      cwd: repoRoot,
      encoding: "utf8",
      stdio: ["ignore", "pipe", "ignore"],
    }).trim();
  } catch {
    return null;
  }
}