// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.

// @ts-check

import { core } from "ext:core/mod.js";
const {
  op_lint_get_rule,
  op_lint_get_source,
  op_lint_report,
} = core.ops;

// Keep in sync with Rust
const AST_PROP_TYPE = 0;
const AST_PROP_PARENT = 1;
const AST_PROP_RANGE = 2;

// Keep in sync with Rust
/** @enum {number} */
const PropFlags = {
  Ref: 0,
  RefArr: 1,
  String: 2,
  Bool: 3,
  Null: 4,
  Undefined: 5,
};

/**
 * @typedef {{
 *   buf: Uint8Array,
 *   strTable: Map<number, string>,
 *   strTableOffset: number,
 *   rootId: number,
 *   nodes: Map<number, Node>,
 *   strByType: number[],
 *   typeByStr: Map<string, number>,
 *   strByProp: number[]
 * }} AstContext
 */

/**
 * @typedef {{
 *   plugins: Deno.LintPlugin[],
 *   installedPlugins: Set<string>,
 * }} LintState
 */

/** @type {LintState} */
const state = {
  plugins: [],
  installedPlugins: new Set(),
};

/** @implements {Deno.LintRuleContext} */
export class Context {
  id;

  fileName;

  #source = null;

  /**
   * @param {string} id
   * @param {string} fileName
   */
  constructor(id, fileName) {
    this.id = id;
    this.fileName = fileName;
  }

  source() {
    if (this.#source === null) {
      this.#source = op_lint_get_source();
    }
    return /** @type {*} */ (this.#source);
  }

  report(data) {
    const range = data.node ? data.node.range : data.range ? data.range : null;
    if (range == null) {
      throw new Error(
        "Either `node` or `span` must be provided when reporting an error",
      );
    }

    const start = range[0] - 1;
    const end = range[1] - 1;

    op_lint_report(
      this.id,
      this.fileName,
      data.message,
      start,
      end,
    );
  }
}

/**
 * @param {Deno.LintPlugin} plugin
 */
export function installPlugin(plugin) {
  if (typeof plugin !== "object") {
    throw new Error("Linter plugin must be an object");
  }
  if (typeof plugin.name !== "string") {
    throw new Error("Linter plugin name must be a string");
  }
  if (typeof plugin.rules !== "object") {
    throw new Error("Linter plugin rules must be an object");
  }
  if (state.installedPlugins.has(plugin.name)) {
    throw new Error(`Linter plugin ${plugin.name} has already been registered`);
  }
  state.plugins.push(plugin);
  state.installedPlugins.add(plugin.name);
}

/**
 * @param {AstContext} ctx
 * @param {number} offset
 * @returns
 */
function getNode(ctx, offset) {
  if (offset === 0) return null;

  const cached = ctx.nodes.get(offset);
  if (cached !== undefined) return cached;

  const node = new Node(ctx, offset);
  ctx.nodes.set(offset, /** @type {*} */ (cached));
  return node;
}

/**
 * @param {Uint8Array} buf
 * @param {number} search
 * @param {number} offset
 * @returns {number}
 */
function findPropOffset(buf, offset, search) {
  // type + parentId + SpanLo + SpanHi
  offset += 1 + 4 + 4 + 4;

  const propCount = buf[offset];
  offset += 1;

  for (let i = 0; i < propCount; i++) {
    const maybe = offset;
    const prop = buf[offset++];
    const kind = buf[offset++];
    if (prop === search) return maybe;

    if (kind === PropFlags.Ref) {
      offset += 4;
    } else if (kind === PropFlags.RefArr) {
      const len = readU32(buf, offset);
      offset += 4 + (len * 4);
    } else if (kind === PropFlags.String) {
      offset += 4;
    } else if (kind === PropFlags.Bool) {
      offset++;
    } else if (kind === PropFlags.Null || kind === PropFlags.Undefined) {
      // No value
    } else {
      offset++;
    }
  }

  return -1;
}

/**
 * @param {AstContext} ctx
 * @param {number} offset
 * @param {number} search
 * @returns {*}
 */
function readValue(ctx, offset, search) {
  const { buf } = ctx;
  const type = buf[offset];

  if (search === AST_PROP_TYPE) {
    return getString(ctx, ctx.strByType[type]);
  } else if (search === AST_PROP_RANGE) {
    const start = readU32(buf, offset + 1 + 4);
    const end = readU32(buf, offset + 1 + 4 + 4);
    return [start, end];
  } else if (search === AST_PROP_PARENT) {
    const pos = readU32(buf, offset + 1);
    return getNode(ctx, pos);
  }

  offset = findPropOffset(ctx.buf, offset, search);
  if (offset === -1) return undefined;

  const kind = buf[offset + 1];

  if (kind === PropFlags.Ref) {
    const value = readU32(buf, offset + 2);
    return getNode(ctx, value);
  } else if (kind === PropFlags.RefArr) {
    const len = readU32(buf, offset);
    offset += 4;

    const nodes = new Array(len);
    for (let i = 0; i < len; i++) {
      nodes[i] = getNode(ctx, readU32(buf, offset));
      offset += 4;
    }
    return nodes;
  } else if (kind === PropFlags.Bool) {
    return buf[offset] === 1;
  } else if (kind === PropFlags.String) {
    const v = readU32(buf, offset);
    return getString(ctx, v);
  } else if (kind === PropFlags.Null) {
    return null;
  } else if (kind === PropFlags.Undefined) {
    return undefined;
  }

  throw new Error(`Unknown prop kind: ${kind}`);
}

/**
 * @param {AstContext} ctx
 * @param {number} offset
 * @returns {*}
 */
function toJsValue(ctx, offset) {
  const { buf } = ctx;

  /** @type {Record<string, any>} */
  const node = {
    type: readValue(ctx, offset, AST_PROP_TYPE),
    range: readValue(ctx, offset, AST_PROP_RANGE),
  };

  // type + parentId + SpanLo + SpanHi
  offset += 1 + 4 + 4 + 4;

  const count = buf[offset++];
  for (let i = 0; i < count; i++) {
    const prop = buf[offset++];
    const kind = buf[offset++];
    const name = getString(ctx, ctx.strByProp[prop]);

    if (kind === PropFlags.Ref) {
      const v = readU32(buf, offset);
      offset += 4;
      node[name] = v === 0 ? null : toJsValue(ctx, v);
    } else if (kind === PropFlags.RefArr) {
      const len = readU32(buf, offset);
      offset += 4;
      const nodes = new Array(len);
      for (let i = 0; i < len; i++) {
        const v = readU32(buf, offset);
        if (v === 0) continue;
        nodes[i] = toJsValue(ctx, v);
        offset += 4;
      }
      node[name] = nodes;
    } else if (kind === PropFlags.Bool) {
      const v = buf[offset++];
      node[name] = v === 1;
    } else if (kind === PropFlags.String) {
      const v = readU32(buf, offset);
      offset += 4;
      node[name] = getString(ctx, v);
    } else if (kind === PropFlags.Null) {
      node[name] = null;
    } else if (kind === PropFlags.Undefined) {
      node[name] = undefined;
    }
  }

  return node;
}

const INTERNAL_CTX = Symbol("ctx");
const INTERNAL_OFFSET = Symbol("offset");

class Node {
  [INTERNAL_CTX];
  [INTERNAL_OFFSET];

  /**
   * @param {AstContext} ctx
   * @param {number} offset
   */
  constructor(ctx, offset) {
    this[INTERNAL_CTX] = ctx;
    this[INTERNAL_OFFSET] = offset;
  }

  /**
   * @param {*} _
   * @param {*} options
   * @returns {string}
   */
  [Symbol.for("Deno.customInspect")](_, options) {
    const json = toJsValue(this[INTERNAL_CTX], this[INTERNAL_OFFSET]);
    return Deno.inspect(json, options);
  }
}

/** @type {Set<number>} */
const appliedGetters = new Set();

/**
 * @param {AstContext} ctx
 */
function setNodeGetters(ctx) {
  if (appliedGetters.size === ctx.strByProp.length) return;

  for (let i = 0; i < ctx.strByProp.length; i++) {
    const id = ctx.strByProp[i];
    if (id === 0 || appliedGetters.has(i)) continue;
    appliedGetters.add(i);

    const name = getString(ctx, id);

    Object.defineProperty(Node.prototype, name, {
      get() {
        return readValue(this[INTERNAL_CTX], this[INTERNAL_OFFSET], i);
      },
    });
  }
}

const DECODER = new TextDecoder();

/**
 * @param {Uint8Array} buf
 * @param {number} i
 * @returns {number}
 */
function readU32(buf, i) {
  return (buf[i] << 24) + (buf[i + 1] << 16) + (buf[i + 2] << 8) +
    buf[i + 3];
}

/**
 * @param {AstContext} ctx
 * @param {number} id
 * @returns {string}
 */
function getString(ctx, id) {
  const name = ctx.strTable.get(id);
  if (name === undefined) {
    throw new Error(`Missing string id: ${id}`);
  }

  return name;
}

/**
 * @param {Uint8Array} buf
 * @param {AstContext} buf
 */
function createAstContext(buf) {
  /** @type {Map<number, string>} */
  const strTable = new Map();

  // console.log(JSON.stringify(buf, null, 2));

  const typeMapOffset = readU32(buf, buf.length - 16);
  const propMapOffset = readU32(buf, buf.length - 12);
  const strTableOffset = readU32(buf, buf.length - 8);
  const rootId = readU32(buf, buf.length - 4);
  // console.log({ strTableOffset, rootId });

  let offset = strTableOffset;
  const stringCount = readU32(buf, offset);
  offset += 4;

  let id = 0;
  for (let i = 0; i < stringCount; i++) {
    const len = readU32(buf, offset);
    offset += 4;

    const strBytes = buf.slice(offset, offset + len);
    offset += len;
    const s = DECODER.decode(strBytes);
    strTable.set(id, s);
    id++;
  }

  // console.log({ stringCount, strTable, rootId });

  if (strTable.size !== stringCount) {
    throw new Error(
      `Could not deserialize string table. Expected ${stringCount} items, but got ${strTable.size}`,
    );
  }

  offset = typeMapOffset;
  const typeCount = readU32(buf, offset);
  offset += 4;

  const typeByStr = new Map();
  const strByType = new Array(typeCount).fill(0);
  for (let i = 0; i < typeCount; i++) {
    const v = readU32(buf, offset);
    offset += 4;

    // console.log("type: ", i, v, strTable.get(v));
    strByType[i] = v;
    typeByStr.set(strTable.get(v), i);
  }

  offset = propMapOffset;
  const propCount = readU32(buf, offset);
  offset += 4;

  const strByProp = new Array(propCount).fill(0);
  for (let i = 0; i < propCount; i++) {
    const v = readU32(buf, offset);
    offset += 4;

    strByProp[i] = v;
  }

  /** @type {AstContext} */
  const ctx = {
    buf,
    strTable,
    rootId,
    nodes: new Map(),
    strTableOffset,
    strByProp,
    strByType,
    typeByStr,
  };

  setNodeGetters(ctx);

  // _dump(ctx);

  return ctx;
}

/**
 * @param {string} fileName
 * @param {Uint8Array} serializedAst
 */
export function runPluginsForFile(fileName, serializedAst) {
  const ctx = createAstContext(serializedAst);
  // console.log(JSON.stringify(ctx, null, 2));

  /** @type {Record<string, (node: any) => void>} */
  const mergedVisitor = {};
  const destroyFns = [];

  // console.log(state);

  // Instantiate and merge visitors. This allows us to only traverse
  // the AST once instead of per plugin.
  for (let i = 0; i < state.plugins.length; i++) {
    const plugin = state.plugins[i];

    for (const name of Object.keys(plugin.rules)) {
      const rule = plugin.rules[name];
      const id = `${plugin.name}/${name}`;
      const ctx = new Context(id, fileName);
      const visitor = rule.create(ctx);

      // console.log({ visitor });

      for (const name in visitor) {
        const prev = mergedVisitor[name];
        mergedVisitor[name] = (node) => {
          if (typeof prev === "function") {
            prev(node);
          }

          try {
            visitor[name](node);
          } catch (err) {
            // FIXME: console here doesn't support error cause
            console.log(err);
            throw new Error(`Visitor "${name}" of plugin "${id}" errored`, {
              cause: err,
            });
          }
        };
      }

      if (typeof rule.destroy === "function") {
        const destroyFn = rule.destroy.bind(rule);
        destroyFns.push(() => {
          try {
            destroyFn(ctx);
          } catch (err) {
            throw new Error(`Destroy hook of "${id}" errored`, { cause: err });
          }
        });
      }
    }
  }

  // Traverse ast with all visitors at the same time to avoid traversing
  // multiple times.
  try {
    traverse(ctx, mergedVisitor);
  } finally {
    ctx.nodes.clear();

    // Optional: Destroy rules
    for (let i = 0; i < destroyFns.length; i++) {
      destroyFns[i]();
    }
  }
}

/**
 * @param {AstContext} ctx
 * @param {*} visitor
 * @returns {void}
 */
function traverse(ctx, visitor) {
  const visitTypes = new Map();

  // TODO: create visiting types
  for (const name in visitor) {
    const id = ctx.typeByStr.get(name);
    if (id === undefined) continue;
    visitTypes.set(id, name);
  }

  console.log("merged visitor", visitor);
  console.log("visiting types", visitTypes);

  traverseInner(ctx, visitTypes, visitor, ctx.rootId);
}

/**
 * @param {AstContext} ctx
 * @param {Map<number, string>} visitTypes
 * @param {Record<string, (x: any) => void>} visitor
 * @param {number} offset
 */
function traverseInner(ctx, visitTypes, visitor, offset) {
  // console.log("traversing offset", offset);

  // Empty id
  if (offset === 0) return;
  const { buf } = ctx;
  const type = buf[offset];

  const name = visitTypes.get(type);
  if (name !== undefined) {
    // console.log("--> invoking visitor");
    const node = new Node(ctx, offset);
    visitor[name](node);
  }

  // type + parentId + SpanLo + SpanHi
  offset += 1 + 4 + 4 + 4;

  const propCount = buf[offset];
  offset += 1;
  // console.log({ propCount });

  for (let i = 0; i < propCount; i++) {
    const kind = buf[offset + 1];
    offset += 2; // propId + propFlags

    if (kind === PropFlags.Ref) {
      const next = readU32(buf, offset);
      offset += 4;
      traverseInner(ctx, visitTypes, visitor, next);
    } else if (kind === PropFlags.RefArr) {
      const len = readU32(buf, offset);
      offset += 4;

      for (let j = 0; j < len; j++) {
        const chiild = readU32(buf, offset);
        offset += 4;
        traverseInner(ctx, visitTypes, visitor, chiild);
      }
    } else if (kind === PropFlags.String) {
      offset += 4;
    } else if (kind === PropFlags.Bool) {
      offset += 1;
    } else if (kind === PropFlags.Null || kind === PropFlags.Undefined) {
      // No value
    }
  }
}

/**
 * @param {AstContext} ctx
 */
function _dump(ctx) {
  const { buf, strTableOffset, strTable, strByType, strByProp } = ctx;

  // @ts-ignore dump fn
  console.log(strTable);

  for (let i = 0; i < strByType.length; i++) {
    const v = strByType[i];
    // @ts-ignore dump fn
    if (v > 0) console.log(" > type:", i, getString(ctx, v), v);
  }
  // @ts-ignore dump fn
  console.log();
  for (let i = 0; i < strByProp.length; i++) {
    const v = strByProp[i];
    // @ts-ignore dump fn
    if (v > 0) console.log(" > prop:", i, getString(ctx, v), v);
  }
  // @ts-ignore dump fn
  console.log();

  let offset = 0;

  while (offset < strTableOffset) {
    const type = buf[offset];
    const name = getString(ctx, ctx.strByType[type]);
    // @ts-ignore dump fn
    console.log(`${name}, offset: ${offset}, type: ${type}`);
    offset += 1;

    const parent = readU32(buf, offset);
    offset += 4;
    // @ts-ignore dump fn
    console.log(`  parent: ${parent}`);

    const start = readU32(buf, offset);
    offset += 4;
    const end = readU32(buf, offset);
    offset += 4;
    // @ts-ignore dump fn
    console.log(`  range: ${start} -> ${end}`);

    const count = buf[offset++];
    // @ts-ignore dump fn
    console.log(`  prop count: ${count}`);

    for (let i = 0; i < count; i++) {
      const prop = buf[offset++];
      const kind = buf[offset++];
      const name = getString(ctx, ctx.strByProp[prop]);

      let kindName = "unknown";
      for (const k in PropFlags) {
        // @ts-ignore dump fn
        if (kind === PropFlags[k]) {
          kindName = k;
        }
      }

      if (kind === PropFlags.Ref) {
        const v = readU32(buf, offset);
        offset += 4;
        // @ts-ignore dump fn
        console.log(`    ${name}: ${v} (${kindName}, ${prop})`);
      } else if (kind === PropFlags.RefArr) {
        const len = readU32(buf, offset);
        offset += 4;
        // @ts-ignore dump fn
        console.log(`    ${name}: Array(${len}) (${kindName}, ${prop})`);

        for (let j = 0; j < len; j++) {
          const v = readU32(buf, offset);
          offset += 4;
          // @ts-ignore dump fn
          console.log(`      - ${v} (${prop})`);
        }
      } else if (kind === PropFlags.Bool) {
        const v = buf[offset];
        offset += 1;
        // @ts-ignore dump fn
        console.log(`    ${name}: ${v} (${kindName}, ${prop})`);
      } else if (kind === PropFlags.String) {
        const v = readU32(buf, offset);
        offset += 4;
        // @ts-ignore dump fn
        console.log(`    ${name}: ${getString(ctx, v)} (${kindName}, ${prop})`);
      } else if (kind === PropFlags.Null) {
        // @ts-ignore dump fn
        console.log(`    ${name}: null (${kindName}, ${prop})`);
      } else if (kind === PropFlags.Undefined) {
        // @ts-ignore dump fn
        console.log(`    ${name}: undefined (${kindName}, ${prop})`);
      }
    }
  }
}