import { DiagnosticCollector, compilerAssert, createDiagnosticCollector } from "./diagnostics.js";
import { getLocationContext } from "./index.js";
import { createDiagnostic } from "./messages.js";
import { Program } from "./program.js";
import { EventEmitter, mapEventEmitterToNodeListener, navigateProgram } from "./semantic-walker.js";
import {
  Diagnostic,
  DiagnosticMessages,
  LibraryInstance,
  LinterRule,
  LinterRuleContext,
  LinterRuleDiagnosticReport,
  LinterRuleSet,
  NoTarget,
  RuleRef,
  SemanticNodeListener,
} from "./types.js";

export interface Linter {
  extendRuleSet(ruleSet: LinterRuleSet): Promise<readonly Diagnostic[]>;
  lint(): readonly Diagnostic[];
}

export function createLinter(
  program: Program,
  loadLibrary: (name: string) => Promise<LibraryInstance | undefined>
): Linter {
  const tracer = program.tracer.sub("linter");

  const ruleMap = new Map<string, LinterRule<string, any>>();
  const enabledRules = new Map<string, LinterRule<string, any>>();
  const linterLibraries = new Map<string, LibraryInstance | undefined>();

  return {
    extendRuleSet,
    lint,
  };

  async function extendRuleSet(ruleSet: LinterRuleSet): Promise<readonly Diagnostic[]> {
    tracer.trace("extend-rule-set.start", JSON.stringify(ruleSet, null, 2));
    const diagnostics = createDiagnosticCollector();
    if (ruleSet.extends) {
      for (const extendingRuleSetName of ruleSet.extends) {
        const ref = diagnostics.pipe(parseRuleReference(extendingRuleSetName));
        if (ref) {
          const library = await resolveLibrary(ref.libraryName);
          const extendingRuleSet = library?.definition?.linter?.ruleSets?.[ref.name];
          if (extendingRuleSet) {
            await extendRuleSet(extendingRuleSet);
          } else {
            diagnostics.add(
              createDiagnostic({
                code: "unknown-rule-set",
                format: { libraryName: ref.libraryName, ruleSetName: ref.name },
                target: NoTarget,
              })
            );
          }
        }
      }
    }

    const enabledInThisRuleSet = new Set<string>();
    if (ruleSet.enable) {
      for (const [ruleName, enable] of Object.entries(ruleSet.enable)) {
        if (enable === false) {
          continue;
        }
        const ref = diagnostics.pipe(parseRuleReference(ruleName as RuleRef));
        if (ref) {
          await resolveLibrary(ref.libraryName);
          const rule = ruleMap.get(ruleName);
          if (rule) {
            enabledInThisRuleSet.add(ruleName);
            enabledRules.set(ruleName, rule);
          } else {
            diagnostics.add(
              createDiagnostic({
                code: "unknown-rule",
                format: { libraryName: ref.libraryName, ruleName: ref.name },
                target: NoTarget,
              })
            );
          }
        }
      }
    }

    if (ruleSet.disable) {
      for (const ruleName of Object.keys(ruleSet.disable)) {
        if (enabledInThisRuleSet.has(ruleName)) {
          diagnostics.add(
            createDiagnostic({
              code: "rule-enabled-disabled",
              format: { ruleName },
              target: NoTarget,
            })
          );
        }
        enabledRules.delete(ruleName);
      }
    }
    tracer.trace(
      "extend-rule-set.end",
      "Rules enabled: \n" + [...enabledRules.keys()].map((x) => ` - ${x}`).join("\n")
    );

    return diagnostics.diagnostics;
  }

  function lint(): readonly Diagnostic[] {
    const diagnostics = createDiagnosticCollector();
    const eventEmitter = new EventEmitter<SemanticNodeListener>();
    tracer.trace(
      "lint",
      `Running linter with following rules:\n` +
        [...enabledRules.keys()].map((x) => ` - ${x}`).join("\n")
    );

    for (const rule of enabledRules.values()) {
      const listener = rule.create(createLinterRuleContext(program, rule, diagnostics));
      for (const [name, cb] of Object.entries(listener)) {
        eventEmitter.on(name as any, cb as any);
      }
    }
    navigateProgram(program, mapEventEmitterToNodeListener(eventEmitter));
    return diagnostics.diagnostics;
  }

  async function resolveLibrary(name: string): Promise<LibraryInstance | undefined> {
    const loadedLibrary = linterLibraries.get(name);
    if (loadedLibrary === undefined) {
      return registerLinterLibrary(name);
    }
    return loadedLibrary;
  }

  async function registerLinterLibrary(name: string): Promise<LibraryInstance | undefined> {
    tracer.trace("register-library", name);

    const library = await loadLibrary(name);
    if (library?.definition?.linter?.rules) {
      for (const ruleDef of library.definition.linter.rules) {
        const ruleId = `${name}/${ruleDef.name}`;
        tracer.trace(
          "register-library.rule",
          `Registering rule "${ruleId}" for library "${name}".`
        );
        const rule: LinterRule<string, any> = { ...ruleDef, id: ruleId };
        if (ruleMap.has(ruleId)) {
          compilerAssert(false, `Unexpected duplicate linter rule: "${ruleId}"`);
        } else {
          ruleMap.set(ruleId, rule);
        }
      }
    }
    linterLibraries.set(name, library);

    return library;
  }

  function parseRuleReference(
    ref: RuleRef
  ): [{ libraryName: string; name: string } | undefined, readonly Diagnostic[]] {
    const segments = ref.split("/");
    const name = segments.pop();
    const libraryName = segments.join("/");
    if (!libraryName || !name) {
      return [
        undefined,
        [createDiagnostic({ code: "invalid-rule-ref", format: { ref }, target: NoTarget })],
      ];
    }
    return [{ libraryName, name }, []];
  }
}

export function createLinterRuleContext<N extends string, DM extends DiagnosticMessages>(
  program: Program,
  rule: LinterRule<N, DM>,
  diagnosticCollector: DiagnosticCollector
): LinterRuleContext<DM> {
  return {
    program,
    reportDiagnostic,
  };

  function createDiagnostic<M extends keyof DM>(
    diag: LinterRuleDiagnosticReport<DM, M>
  ): Diagnostic {
    const message = rule.messages[diag.messageId ?? "default"];
    if (!message) {
      const messageString = Object.keys(rule.messages)
        .map((x) => ` - ${x}`)
        .join("\n");
      const messageId = String(diag.messageId);
      throw new Error(
        `Unexpected message id '${messageId}' for rule '${rule.name}'. Defined messages:\n${messageString}`
      );
    }

    const messageStr = typeof message === "string" ? message : message((diag as any).format);

    return {
      code: rule.id,
      severity: rule.severity,
      message: messageStr,
      target: diag.target,
    };
  }

  function reportDiagnostic<M extends keyof DM>(diag: LinterRuleDiagnosticReport<DM, M>): void {
    const diagnostic = createDiagnostic(diag);
    if (diagnostic.target !== NoTarget) {
      const context = getLocationContext(program, diagnostic.target);
      // Only report diagnostic in the user project.
      // See for showing diagnostic in library at point of usage https://github.com/microsoft/typespec/issues/1997
      if (context.type === "project") {
        diagnosticCollector.add(diagnostic);
      }
    }
  }
}
