Initial project setup

Partly ported from actions/setup-ruby

src/installer.ts

@@ -0,0 +1,54 @@
+import * as core from '@actions/core';
+import * as exec from '@actions/exec';
+import * as tc from '@actions/tool-cache';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as semver from 'semver';
+
+export async function cacheHaskellTool(installDir: string, tool: string) {
+  const baseGHCDir: string = path.join(installDir, tool);
+  const versions: string[] = fs.readdirSync(baseGHCDir);
+  for (const v of versions) {
+    const version = normalizeVersion(v);
+    core.debug(`found ${tool} version: ${v} normalized to ${version}`);
+    const dir: string = path.join(baseGHCDir, v);
+    await tc.cacheDir(dir, tool, version);
+  }
+}
+
+export async function findHaskellGHCVersion(version: string) {
+  return _findHaskellToolVersion('ghc', version);
+}
+
+export async function findHaskellCabalVersion(version: string) {
+  return _findHaskellToolVersion('cabal', version);
+}
+
+export async function _findHaskellToolVersion(tool: string, version: string) {
+  version = normalizeVersion(version);
+  const installDir: string | null = tc.find(tool, version);
+  if (!installDir) {
+    throw new Error(`Version ${version} of ${tool} not found`);
+  }
+
+  const toolPath: string = path.join(installDir, 'bin');
+
+  core.addPath(toolPath);
+}
+
+// This function is required to convert the version 1.10 to 1.10.0.
+// Because caching utility accept only sementic version,
+// which have patch number as well.
+function normalizeVersion(version: string): string {
+  const versionPart = version.split('.');
+  if (versionPart[1] == null) {
+    //append minor and patch version if not available
+    return version.concat('.0.0');
+  }
+  if (versionPart[2] == null) {
+    //append patch version if not available
+    return version.concat('.0');
+  }
+
+  return version;
+}

src/setup-haskell.ts

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+import * as core from '@actions/core';
+import {findHaskellGHCVersion, cacheHaskellTool} from './installer';
+
+async function run() {
+  try {
+    await cacheHaskellTool('/opt', 'ghc');
+    await cacheHaskellTool('/opt', 'cabal');
+    let ghcVersion = core.getInput('ghc-version');
+    await findHaskellGHCVersion(ghcVersion);
+  } catch (error) {
+    core.setFailed(error.message);
+  }
+}
+
+run();