/**
 * Implements RAM Calculation functionality.
 *
 * Uses the acorn.js library to parse a script's code into an AST and
 * recursively walk through that AST, calculating RAM usage along
 * the way
 */
import * as walk from "acorn-walk";
import { parse } from "acorn";

import { RamCalculationErrorCode } from "./RamCalculationErrorCodes";

import { RamCosts, RamCostConstants } from "../Netscript/RamCostGenerator";

// These special strings are used to reference the presence of a given logical
// construct within a user script.
const specialReferenceIF = "__SPECIAL_referenceIf";
const specialReferenceFOR = "__SPECIAL_referenceFor";
const specialReferenceWHILE = "__SPECIAL_referenceWhile";

// The global scope of a script is registered under this key during parsing.
const memCheckGlobalKey = ".__GLOBAL__";

/**
 * Parses code into an AST and walks through it recursively to calculate
 * RAM usage. Also accounts for imported modules.
 * @param {Script[]} otherScripts - All other scripts on the server. Used to account for imported scripts
 * @param {string} codeCopy - The code being parsed
 * @param {WorkerScript} workerScript - Object containing RAM costs of Netscript functions. Also used to
 *                                      keep track of what functions have/havent been accounted for
 */
async function parseOnlyRamCalculate(otherScripts, code, workerScript) {
  try {
    /**
     * Maps dependent identifiers to their dependencies.
     *
     * The initial identifier is __SPECIAL_INITIAL_MODULE__.__GLOBAL__.
     * It depends on all the functions declared in the module, all the global scopes
     * of its imports, and any identifiers referenced in this global scope. Each
     * function depends on all the identifiers referenced internally.
     * We walk the dependency graph to calculate RAM usage, given that some identifiers
     * reference Netscript functions which have a RAM cost.
     */
    let dependencyMap = {};

    // Scripts we've parsed.
    const completedParses = new Set();

    // Scripts we've discovered that need to be parsed.
    const parseQueue = [];

    // Parses a chunk of code with a given module name, and updates parseQueue and dependencyMap.
    function parseCode(code, moduleName) {
      const result = parseOnlyCalculateDeps(code, moduleName);
      completedParses.add(moduleName);

      // Add any additional modules to the parse queue;
      for (let i = 0; i < result.additionalModules.length; ++i) {
        if (!completedParses.has(result.additionalModules[i])) {
          parseQueue.push(result.additionalModules[i]);
        }
      }

      // Splice all the references in
      dependencyMap = Object.assign(dependencyMap, result.dependencyMap);
    }

    // Parse the initial module, which is the "main" script that is being run
    const initialModule = "__SPECIAL_INITIAL_MODULE__";
    parseCode(code, initialModule);

    // Process additional modules, which occurs if the "main" script has any imports
    while (parseQueue.length > 0) {
      const nextModule = parseQueue.shift();

      // Additional modules can either be imported from the web (in which case we use
      // a dynamic import), or from other in-game scripts
      let code;
      if (nextModule.startsWith("https://") || nextModule.startsWith("http://")) {
        try {
          // eslint-disable-next-line no-await-in-loop
          const module = await eval("import(nextModule)");
          code = "";
          for (const prop in module) {
            if (typeof module[prop] === "function") {
              code += module[prop].toString() + ";\n";
            }
          }
        } catch (e) {
          console.error(`Error dynamically importing module from ${nextModule} for RAM calculations: ${e}`);
          return RamCalculationErrorCode.URLImportError;
        }
      } else {
        if (!Array.isArray(otherScripts)) {
          console.warn(`parseOnlyRamCalculate() not called with array of scripts`);
          return RamCalculationErrorCode.ImportError;
        }

        let script = null;
        let fn = nextModule.startsWith("./") ? nextModule.slice(2) : nextModule;
        for (const s of otherScripts) {
          if (s.filename === fn) {
            script = s;
            break;
          }
        }

        if (script == null) {
          return RamCalculationErrorCode.ImportError; // No such script on the server
        }

        code = script.code;
      }

      parseCode(code, nextModule);
    }

    // Finally, walk the reference map and generate a ram cost. The initial set of keys to scan
    // are those that start with __SPECIAL_INITIAL_MODULE__.
    let ram = RamCostConstants.ScriptBaseRamCost;
    const unresolvedRefs = Object.keys(dependencyMap).filter((s) => s.startsWith(initialModule));
    const resolvedRefs = new Set();
    while (unresolvedRefs.length > 0) {
      const ref = unresolvedRefs.shift();

      // Check if this is one of the special keys, and add the appropriate ram cost if so.
      if (ref === "hacknet" && !resolvedRefs.has("hacknet")) {
        ram += RamCostConstants.ScriptHacknetNodesRamCost;
      }
      if (ref === "document" && !resolvedRefs.has("document")) {
        ram += RamCostConstants.ScriptDomRamCost;
      }
      if (ref === "window" && !resolvedRefs.has("window")) {
        ram += RamCostConstants.ScriptDomRamCost;
      }

      resolvedRefs.add(ref);

      if (ref.endsWith(".*")) {
        // A prefix reference. We need to find all matching identifiers.
        const prefix = ref.slice(0, ref.length - 2);
        for (let ident of Object.keys(dependencyMap).filter((k) => k.startsWith(prefix))) {
          for (let dep of dependencyMap[ident] || []) {
            if (!resolvedRefs.has(dep)) unresolvedRefs.push(dep);
          }
        }
      } else {
        // An exact reference. Add all dependencies of this ref.
        for (let dep of dependencyMap[ref] || []) {
          if (!resolvedRefs.has(dep)) unresolvedRefs.push(dep);
        }
      }

      // Check if this identifier is a function in the workerScript environment.
      // If it is, then we need to get its RAM cost.
      try {
        function applyFuncRam(func) {
          if (typeof func === "function") {
            try {
              let res;
              if (func.constructor.name === "AsyncFunction") {
                res = 0; // Async functions will always be 0 RAM
              } else {
                res = func.apply(null, []);
              }
              if (typeof res === "number") {
                return res;
              }
              return 0;
            } catch (e) {
              console.error(`Error applying function: ${e}`);
              return 0;
            }
          } else {
            return 0;
          }
        }

        // Only count each function once
        if (workerScript.loadedFns[ref]) {
          continue;
        } else {
          workerScript.loadedFns[ref] = true;
        }

        // This accounts for namespaces (Bladeburner, CodingCpntract, etc.)
        let func;
        if (ref in workerScript.env.vars.bladeburner) {
          func = workerScript.env.vars.bladeburner[ref];
        } else if (ref in workerScript.env.vars.codingcontract) {
          func = workerScript.env.vars.codingcontract[ref];
        } else if (ref in workerScript.env.vars.gang) {
          func = workerScript.env.vars.gang[ref];
        } else if (ref in workerScript.env.vars.sleeve) {
          func = workerScript.env.vars.sleeve[ref];
        } else {
          func = workerScript.env.vars[ref];
        }
        ram += applyFuncRam(func);
      } catch (error) {
        continue;
      }
    }
    return ram;
  } catch (error) {
    // console.info("parse or eval error: ", error);
    // This is not unexpected. The user may be editing a script, and it may be in
    // a transitory invalid state.
    return RamCalculationErrorCode.SyntaxError;
  }
}

/**
 * Helper function that parses a single script. It returns a map of all dependencies,
 * which are items in the code's AST that potentially need to be evaluated
 * for RAM usage calculations. It also returns an array of additional modules
 * that need to be parsed (i.e. are 'import'ed scripts).
 */
function parseOnlyCalculateDeps(code, currentModule) {
  const ast = parse(code, { sourceType: "module", ecmaVersion: "latest" });

  // Everything from the global scope goes in ".". Everything else goes in ".function", where only
  // the outermost layer of functions counts.
  const globalKey = currentModule + memCheckGlobalKey;
  const dependencyMap = {};
  dependencyMap[globalKey] = new Set();

  // If we reference this internal name, we're really referencing that external name.
  // Filled when we import names from other modules.
  let internalToExternal = {};

  var additionalModules = [];

  // References get added pessimistically. They are added for thisModule.name, name, and for
  // any aliases.
  function addRef(key, name) {
    const s = dependencyMap[key] || (dependencyMap[key] = new Set());
    if (name in internalToExternal) {
      s.add(internalToExternal[name]);
    }
    s.add(currentModule + "." + name);
    s.add(name); // For builtins like hack.
  }

  //A list of identifiers that resolve to "native Javascript code"
  const objectPrototypeProperties = Object.getOwnPropertyNames(Object.prototype);

  // If we discover a dependency identifier, state.key is the dependent identifier.
  // walkDeeper is for doing recursive walks of expressions in composites that we handle.
  function commonVisitors() {
    return {
      Identifier: (node, st) => {
        if (objectPrototypeProperties.includes(node.name)) {
          return;
        }
        addRef(st.key, node.name);
      },
      WhileStatement: (node, st, walkDeeper) => {
        addRef(st.key, specialReferenceWHILE);
        node.test && walkDeeper(node.test, st);
        node.body && walkDeeper(node.body, st);
      },
      DoWhileStatement: (node, st, walkDeeper) => {
        addRef(st.key, specialReferenceWHILE);
        node.test && walkDeeper(node.test, st);
        node.body && walkDeeper(node.body, st);
      },
      ForStatement: (node, st, walkDeeper) => {
        addRef(st.key, specialReferenceFOR);
        node.init && walkDeeper(node.init, st);
        node.test && walkDeeper(node.test, st);
        node.update && walkDeeper(node.update, st);
        node.body && walkDeeper(node.body, st);
      },
      IfStatement: (node, st, walkDeeper) => {
        addRef(st.key, specialReferenceIF);
        node.test && walkDeeper(node.test, st);
        node.consequent && walkDeeper(node.consequent, st);
        node.alternate && walkDeeper(node.alternate, st);
      },
      MemberExpression: (node, st, walkDeeper) => {
        node.object && walkDeeper(node.object, st);
        node.property && walkDeeper(node.property, st);
      },
    };
  }

  walk.recursive(
    ast,
    { key: globalKey },
    Object.assign(
      {
        ImportDeclaration: (node, st) => {
          const importModuleName = node.source.value;
          additionalModules.push(importModuleName);

          // This module's global scope refers to that module's global scope, no matter how we
          // import it.
          dependencyMap[st.key].add(importModuleName + memCheckGlobalKey);

          for (let i = 0; i < node.specifiers.length; ++i) {
            const spec = node.specifiers[i];
            if (spec.imported !== undefined && spec.local !== undefined) {
              // We depend on specific things.
              internalToExternal[spec.local.name] = importModuleName + "." + spec.imported.name;
            } else {
              // We depend on everything.
              dependencyMap[st.key].add(importModuleName + ".*");
            }
          }
        },
        FunctionDeclaration: (node) => {
          const key = currentModule + "." + node.id.name;
          walk.recursive(node, { key: key }, commonVisitors());
        },
      },
      commonVisitors(),
    ),
  );

  return { dependencyMap: dependencyMap, additionalModules: additionalModules };
}

/**
 * Calculate's a scripts RAM Usage
 * @param {string} codeCopy - The script's code
 * @param {Script[]} otherScripts - All other scripts on the server.
 *                                  Used to account for imported scripts
 */
export async function calculateRamUsage(codeCopy, otherScripts) {
  // We don't need a real WorkerScript for this. Just an object that keeps
  // track of whatever's needed for RAM calculations
  const workerScript = {
    loadedFns: {},
    env: {
      vars: RamCosts,
    },
  };

  try {
    return await parseOnlyRamCalculate(otherScripts, codeCopy, workerScript);
  } catch (e) {
    console.error(`Failed to parse script for RAM calculations:`);
    console.error(e);
    return RamCalculationErrorCode.SyntaxError;
  }

  return RamCalculationErrorCode.SyntaxError;
}
