import type { Program } from "./program.js";
import { createSourceFile } from "./source-file.js";
import {
  CodeFix,
  Diagnostic,
  DiagnosticResult,
  DiagnosticTarget,
  LogSink,
  Node,
  NodeFlags,
  NoTarget,
  RelatedSourceLocation,
  SourceLocation,
  SymbolFlags,
  SyntaxKind,
  Type,
  TypeSpecDiagnosticTarget,
} from "./types.js";

export type WriteLine = (text?: string) => void;
export type DiagnosticHandler = (diagnostic: Diagnostic) => void;

export function logDiagnostics(diagnostics: readonly Diagnostic[], logger: LogSink) {
  for (const diagnostic of diagnostics) {
    logger.log({
      level: diagnostic.severity,
      message: diagnostic.message,
      code: diagnostic.code,
      url: diagnostic.url,
      sourceLocation: getSourceLocation(diagnostic.target, { locateId: true }),
      related: getRelatedLocations(diagnostic),
    });
  }
}

/** @internal */
export function getRelatedLocations(diagnostic: Diagnostic): RelatedSourceLocation[] {
  return getDiagnosticTemplateInstantitationTrace(diagnostic.target).map((x) => {
    return {
      message: "occurred while instantiating template",
      location: getSourceLocation(x),
    };
  });
}

/**
 * Find the syntax node for a TypeSpec diagnostic target.
 *
 * This function extracts the AST node from various types of diagnostic targets:
 * - For template instance targets: returns the node of the template declaration
 * - For symbols: returns the first declaration node (or symbol source for using symbols)
 * - For AST nodes: returns the node itself
 * - For types: returns the node associated with the type
 *
 * @param target The diagnostic target to extract a node from. Can be a template instance,
 *               symbol, AST node, or type.
 * @returns The AST node associated with the target, or undefined if the target is a type
 *          or symbol that doesn't have an associated node.
 */
export function getNodeForTarget(target: TypeSpecDiagnosticTarget): Node | undefined {
  if (!("kind" in target) && !("entityKind" in target)) {
    // TemplateInstanceTarget
    if (!("declarations" in target)) {
      return target.node;
    }

    // symbol
    if (target.flags & SymbolFlags.Using) {
      target = target.symbolSource!;
    }

    return target.declarations[0];
  } else if ("kind" in target && typeof target.kind === "number") {
    // node
    return target as Node;
  } else {
    // type
    return (target as Type).node;
  }
}

export interface SourceLocationOptions {
  /**
   * If trying to resolve the location of a type with an ID, show the location of the ID node instead of the entire type.
   * This makes sure that the location range is not too large and hard to read.
   */
  locateId?: boolean;
}
export function getSourceLocation(
  target: DiagnosticTarget,
  options?: SourceLocationOptions,
): SourceLocation;
export function getSourceLocation(
  target: typeof NoTarget | undefined,
  options?: SourceLocationOptions,
): undefined;
export function getSourceLocation(
  target: DiagnosticTarget | typeof NoTarget | undefined,
  options?: SourceLocationOptions,
): SourceLocation | undefined;
export function getSourceLocation(
  target: DiagnosticTarget | typeof NoTarget | undefined,
  options: SourceLocationOptions = {},
): SourceLocation | undefined {
  if (target === NoTarget || target === undefined) {
    return undefined;
  }

  if ("file" in target) {
    return target;
  }

  const node = getNodeForTarget(target);
  return node ? getSourceLocationOfNode(node, options) : createSyntheticSourceLocation();
}

/**
 * @internal
 */
export function getDiagnosticTemplateInstantitationTrace(
  target: DiagnosticTarget | typeof NoTarget | undefined,
): Node[] {
  if (typeof target !== "object" || !("templateMapper" in target)) {
    return [];
  }

  const result = [];
  let current = target.templateMapper;
  while (current) {
    result.push(current.source.node);
    current = current.source.mapper;
  }
  return result;
}

function createSyntheticSourceLocation(loc = "<unknown location>") {
  return {
    file: createSourceFile("", loc),
    pos: 0,
    end: 0,
    isSynthetic: true,
  };
}

function getSourceLocationOfNode(node: Node, options: SourceLocationOptions): SourceLocation {
  let root = node;

  while (root.parent !== undefined) {
    root = root.parent;
  }

  if (root.kind !== SyntaxKind.TypeSpecScript && root.kind !== SyntaxKind.JsSourceFile) {
    return createSyntheticSourceLocation(
      node.flags & NodeFlags.Synthetic
        ? undefined
        : "<unknown location - cannot obtain source location of unbound node - file bug at https://github.com/microsoft/typespec>",
    );
  }

  if (options.locateId && "id" in node && node.id !== undefined) {
    node = node.id;
  }

  return {
    file: root.file,
    pos: node.pos,
    end: node.end,
  };
}

/**
 * Verbose output is enabled by default for runs in mocha explorer in VS Code,
 * where the output is nicely associated with the individual test, and disabled
 * by default for command line runs where we don't want to spam the console.
 *
 * If the steps taken to produce the message are expensive, pass a callback
 * instead of producing the message then passing it here only to be dropped
 * when verbose output is disabled.
 */
export function logVerboseTestOutput(
  messageOrCallback: string | ((log: (message: string) => void) => void),
) {
  if (process.env.TYPESPEC_VERBOSE_TEST_OUTPUT) {
    if (typeof messageOrCallback === "string") {
      // eslint-disable-next-line no-console
      console.log(messageOrCallback);
    } else {
      // eslint-disable-next-line no-console
      messageOrCallback(console.log);
    }
  }
}

/**
 * Use this to report bugs in the compiler, and not errors in the source code
 * being compiled.
 *
 * @param condition Throw if this is not true.
 *
 * @param message Error message.
 *
 * @param target Optional location in source code that might give a clue about
 *               what got the compiler off track.
 */
export function compilerAssert(
  condition: any,
  message: string,
  target?: DiagnosticTarget,
): asserts condition {
  if (condition) {
    return;
  }

  if (target) {
    let location: SourceLocation | undefined;
    try {
      location = getSourceLocation(target);
    } catch (err: any) {}

    if (location) {
      const pos = location.file.getLineAndCharacterOfPosition(location.pos);
      const file = location.file.path;
      const line = pos.line + 1;
      const col = pos.character + 1;
      message += `\nOccurred while compiling code in ${file} near line ${line}, column ${col}`;
    }
  }

  throw new Error(message);
}

/**
 * Assert that the input type has one of the kinds provided
 */
export function assertType<TKind extends Type["kind"][]>(
  typeDescription: string,
  t: Type,
  ...kinds: TKind
): asserts t is Type & { kind: TKind[number] } {
  if (kinds.indexOf(t.kind) === -1) {
    throw new Error(`Expected ${typeDescription} to be type ${kinds.join(", ")}`);
  }
}

/**
 * Report a deprecated diagnostic.
 * @param program TypeSpec Program.
 * @param message Message describing the deprecation.
 * @param target Target of the deprecation.
 */
export function reportDeprecated(
  program: Program,
  message: string,
  target: DiagnosticTarget | typeof NoTarget,
): void {
  program.reportDiagnostic({
    severity: "warning",
    code: "deprecated",
    message: `Deprecated: ${message}`,
    target,
  });
}

/**
 * Helper object to collect diagnostics from function following the diagnostics accessor pattern(foo() => [T, Diagnostic[]])
 */
export interface DiagnosticCollector {
  readonly diagnostics: readonly Diagnostic[];

  /**
   * Add a diagnostic to the collection
   * @param diagnostic Diagnostic to add.
   */
  add(diagnostic: Diagnostic): void;

  /**
   * Unwrap the Diagnostic result, add all the diagnostics and return the data.
   * @param result Accessor diagnostic result
   */
  pipe<T>(result: DiagnosticResult<T>): T;

  /**
   * Wrap the given value in a tuple including the diagnostics following the TypeSpec accessor pattern.
   * @param value Accessor value to return
   * @example return diagnostics.wrap(routes);
   */
  wrap<T>(value: T): DiagnosticResult<T>;

  /**
   * Join the given result with the diagnostics in this collector.
   * @param result - result to join with the diagnostics
   * @returns - the result with the combined diagnostics
   */
  join<T>(result: DiagnosticResult<T>): DiagnosticResult<T>;
}

/**
 * Create a new instance of the @see DiagnosticCollector.
 */
export function createDiagnosticCollector(): DiagnosticCollector {
  const diagnostics: Diagnostic[] = [];

  return {
    diagnostics,
    add,
    pipe,
    wrap,
    join,
  };

  function add(diagnostic: Diagnostic) {
    diagnostics.push(diagnostic);
  }

  function pipe<T>(result: DiagnosticResult<T>): T {
    const [value, diags] = result;
    for (const diag of diags) {
      diagnostics.push(diag);
    }
    return value;
  }

  function wrap<T>(value: T): DiagnosticResult<T> {
    return [value, diagnostics];
  }

  function join<T>(result: DiagnosticResult<T>): DiagnosticResult<T> {
    const [value, diags] = result;
    for (const diag of diags) {
      diagnostics.push(diag);
    }
    return [value, diagnostics];
  }
}

/**
 * Ignore the diagnostics emitted by the diagnostic accessor pattern and just return the actual result.
 * @param result Accessor pattern tuple result including the actual result and the list of diagnostics.
 * @returns Actual result.
 */
export function ignoreDiagnostics<T>(result: DiagnosticResult<T>): T {
  return result[0];
}

export function defineCodeFix(fix: CodeFix): CodeFix {
  return fix;
}
