/**
 * Models the `execa` library in terms of `FileSystemAccess` and `SystemCommandExecution`.
 */

import javascript

/**
 * Provide model for [Execa](https://github.com/sindresorhus/execa) package
 */
module Execa {
  /**
   * The Execa input file read and output file write
   */
  class ExecaFileSystemAccess extends FileSystemReadAccess, DataFlow::Node {
    API::Node execaArg;
    boolean isPipedToFile;

    ExecaFileSystemAccess() {
      (
        execaArg = API::moduleImport("execa").getMember("$").getParameter(0) and
        isPipedToFile = false
        or
        execaArg =
          API::moduleImport("execa")
              .getMember(["execa", "execaCommand", "execaCommandSync", "execaSync"])
              .getParameter([0, 1, 2]) and
        isPipedToFile = false
        or
        execaArg =
          API::moduleImport("execa")
              .getMember(["execa", "execaCommand", "execaCommandSync", "execaSync"])
              .getReturn()
              .getMember(["pipeStdout", "pipeAll", "pipeStderr"])
              .getParameter(0) and
        isPipedToFile = true
      ) and
      this = execaArg.asSink()
    }

    override DataFlow::Node getADataNode() { none() }

    override DataFlow::Node getAPathArgument() {
      result = execaArg.getMember("inputFile").asSink() and isPipedToFile = false
      or
      result = execaArg.asSink() and isPipedToFile = true
    }
  }

  /**
   * A call to `execa.execa` or `execa.execaSync`
   */
  class ExecaCall extends API::CallNode {
    boolean isSync;

    ExecaCall() {
      this = API::moduleImport("execa").getMember("execa").getACall() and
      isSync = false
      or
      this = API::moduleImport("execa").getMember("execaSync").getACall() and
      isSync = true
      or
      this = API::moduleImport("execa").getACall() and
      isSync = false
    }
  }

  /**
   * The system command execution nodes for `execa.execa` or `execa.execaSync` functions
   */
  class ExecaExec extends SystemCommandExecution, ExecaCall {
    ExecaExec() { isSync = [false, true] }

    override DataFlow::Node getACommandArgument() { result = this.getArgument(0) }

    override predicate isShellInterpreted(DataFlow::Node arg) {
      // if shell: true then first and second args are sinks
      // options can be third argument
      arg = [this.getArgument(0), this.getParameter(1).getArrayElement().asSink()] and
      isExecaShellEnable(this.getParameter(2))
      or
      // options can be second argument
      arg = this.getArgument(0) and
      isExecaShellEnable(this.getParameter(1))
    }

    override DataFlow::Node getArgumentList() {
      // execa(cmd, [arg]);
      exists(DataFlow::Node arg | arg = this.getArgument(1) |
        // if it is a object then it is a option argument not command argument
        result = arg and not arg.asExpr() instanceof ObjectExpr
      )
    }

    override predicate isSync() { isSync = true }

    override DataFlow::Node getOptionsArg() {
      result = this.getLastArgument() and result.asExpr() instanceof ObjectExpr
    }
  }

  /**
   * A call to `execa.$` or `execa.$.sync` or `execa.$({})` or `execa.$.sync({})` tag functions
   */
  private class ExecaScriptCall extends API::CallNode {
    boolean isSync;

    ExecaScriptCall() {
      exists(API::Node script |
        script =
          [
            API::moduleImport("execa").getMember("$"),
            API::moduleImport("execa").getMember("$").getReturn()
          ]
      |
        this = script.getACall() and
        isSync = false
        or
        this = script.getMember("sync").getACall() and
        isSync = true
      )
    }
  }

  /**
   * The system command execution nodes for `execa.$` or `execa.$.sync` tag functions
   */
  class ExecaScript extends SystemCommandExecution, ExecaScriptCall {
    ExecaScript() { isSync = [false, true] }

    override DataFlow::Node getACommandArgument() {
      result = this.getParameter(1).asSink() and
      not isTaggedTemplateFirstChildAnElement(this.getParameter(1).asSink().asExpr().getParent())
    }

    override predicate isShellInterpreted(DataFlow::Node arg) {
      isExecaShellEnable(this.getParameter(0)) and
      arg = this.getAParameter().asSink()
    }

    override DataFlow::Node getArgumentList() {
      result = this.getParameter(any(int i | i >= 1)).asSink() and
      isTaggedTemplateFirstChildAnElement(this.getParameter(1).asSink().asExpr().getParent())
      or
      result = this.getParameter(any(int i | i >= 2)).asSink() and
      not isTaggedTemplateFirstChildAnElement(this.getParameter(1).asSink().asExpr().getParent())
    }

    override DataFlow::Node getOptionsArg() { result = this.getParameter(0).asSink() }

    override predicate isSync() { isSync = true }
  }

  /**
   * A call to `execa.execaCommandSync` or `execa.execaCommand`
   */
  private class ExecaCommandCall extends API::CallNode {
    boolean isSync;

    ExecaCommandCall() {
      this = API::moduleImport("execa").getMember("execaCommandSync").getACall() and
      isSync = true
      or
      this = API::moduleImport("execa").getMember("execaCommand").getACall() and
      isSync = false
    }
  }

  /**
   * The system command execution nodes for `execa.execaCommand` or `execa.execaCommandSync` functions
   */
  class ExecaCommandExec extends SystemCommandExecution, ExecaCommandCall {
    ExecaCommandExec() { isSync = [false, true] }

    override DataFlow::Node getACommandArgument() {
      result = this.(DataFlow::CallNode).getArgument(0)
    }

    override DataFlow::Node getArgumentList() {
      // execaCommand(`${cmd} ${arg}`);
      result.asExpr() = this.getParameter(0).asSink().asExpr().getAChildExpr() and
      not result.asExpr() = this.getArgument(0).asExpr().getChildExpr(0)
    }

    override predicate isShellInterpreted(DataFlow::Node arg) {
      // execaCommandSync(`${cmd} ${arg}`, {shell: true})
      arg.asExpr() = this.getArgument(0).asExpr().getAChildExpr+() and
      isExecaShellEnable(this.getParameter(1))
      or
      // there is only one argument that is constructed in previous nodes,
      // it makes sanitizing really hard to select whether it is vulnerable to argument injection or not
      arg = this.getParameter(0).asSink() and
      not exists(this.getArgument(0).asExpr().getChildExpr(1))
    }

    override predicate isSync() { isSync = true }

    override DataFlow::Node getOptionsArg() {
      result = this.getLastArgument() and result.asExpr() instanceof ObjectExpr
    }
  }

  /** Gets a TemplateLiteral and check if first child is a template element */
  private predicate isTaggedTemplateFirstChildAnElement(TemplateLiteral templateLit) {
    exists(templateLit.getChildExpr(0).(TemplateElement))
  }

  /**
   * Holds whether Execa has shell enabled options or not, get Parameter responsible for options
   */
  pragma[inline]
  private predicate isExecaShellEnable(API::Node n) {
    n.getMember("shell").asSink().asExpr().(BooleanLiteral).getValue() = "true"
  }

  /**
   * A call to `execa.node`
   */
  class ExecaNodeCall extends SystemCommandExecution, API::CallNode {
    ExecaNodeCall() { this = API::moduleImport("execa").getMember("node").getACall() }

    override DataFlow::Node getACommandArgument() { result = this.getArgument(0) }

    override predicate isShellInterpreted(DataFlow::Node arg) { none() }

    override DataFlow::Node getArgumentList() {
      result = this.getArgument(1) and
      not result.asExpr() instanceof ObjectExpr
    }

    override predicate isSync() { none() }

    override DataFlow::Node getOptionsArg() {
      result = this.getLastArgument() and
      result.asExpr() instanceof ObjectExpr
    }
  }

  /**
   * A call to `execa.stdout`, `execa.stderr`, or `execa.sync`
   */
  class ExecaStreamCall extends SystemCommandExecution, API::CallNode {
    string methodName;

    ExecaStreamCall() {
      methodName in ["stdout", "stderr", "sync"] and
      this = API::moduleImport("execa").getMember(methodName).getACall()
    }

    override DataFlow::Node getACommandArgument() { result = this.getArgument(0) }

    override predicate isShellInterpreted(DataFlow::Node arg) {
      arg = this.getArgument(0) and
      isExecaShellEnable(this.getParameter([1, 2]))
    }

    override DataFlow::Node getArgumentList() {
      result = this.getArgument(1) and
      not result.asExpr() instanceof ObjectExpr
    }

    override predicate isSync() { methodName = "sync" }

    override DataFlow::Node getOptionsArg() {
      result = this.getLastArgument() and
      result.asExpr() instanceof ObjectExpr
    }
  }

  /**
   * A call to `execa.shell` or `execa.shellSync`
   */
  class ExecaShellCall extends SystemCommandExecution, API::CallNode {
    boolean sync;

    ExecaShellCall() {
      this = API::moduleImport("execa").getMember("shell").getACall() and
      sync = false
      or
      this = API::moduleImport("execa").getMember("shellSync").getACall() and
      sync = true
    }

    override DataFlow::Node getACommandArgument() { result = this.getArgument(0) }

    override predicate isShellInterpreted(DataFlow::Node arg) { arg = this.getACommandArgument() }

    override DataFlow::Node getArgumentList() { none() }

    override predicate isSync() { sync = true }

    override DataFlow::Node getOptionsArg() {
      result = this.getArgument(1) and
      result.asExpr() instanceof ObjectExpr
    }
  }
}