package main

// The recipe of the Node build module (novox/hq ADR 0405 §7, ADR 0469 §4, ADR 0477 §1-§3; issues 1488, 1572): the
// recipe's own version, and the recipe version, a hash of that and the bytes of the lock file that names the
// TypeScript toolchain. The module names no Node version: it builds with the installed nodejs and npm, reports the
// version installed to the toolchains state, and refuses only when node cannot be run (module.go).

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"os"
)

// RecipeSteps is the recipe's own version: changed whenever the steps of fetch, test or build change in a way that
// can change what they produce (ADR 0405 §7). It is one of the two values the recipe version hashes.
const RecipeSteps = "1"

// Recipe is every value that makes up the recipe version.
type Recipe struct {
	// Steps is RecipeSteps.
	Steps string
	// Lock is the hex sha256 of the bytes of toolchain/package-lock.json (LockHash).
	Lock string
}

// LockHash is the text a lock file's bytes stand for in the recipe version.
func LockHash(lock []byte) string {
	sum := sha256.Sum256(lock)
	return hex.EncodeToString(sum[:])
}

// ReadRecipe is the recipe of this build of the module with the lock file read from path. A missing lock is an
// error: with no lock there is no toolchain to name.
func ReadRecipe(lockPath string) (Recipe, error) {
	raw, err := os.ReadFile(lockPath)
	if err != nil {
		return Recipe{}, fmt.Errorf("the toolchain's lock file cannot be read: %w", err)
	}
	return Recipe{Steps: RecipeSteps, Lock: LockHash(raw)}, nil
}

// Version is the recipe version: a hash of the recipe's own version and the lock file's hash, never a Node version
// (ADR 0477 §3): the toolchain enters each fingerprint once, as the version the build nodes agree on. A change of
// either moves it and with it every fingerprint that holds it (ADR 0405 §7, ADR 0465 §2). The
// fields are named in the hashed text, so no two recipes share a text.
func (r Recipe) Version() string {
	h := sha256.New()
	for _, f := range [][2]string{{"steps", r.Steps}, {"lock", r.Lock}} {
		h.Write([]byte(f[0] + "=" + f[1] + "\n"))
	}
	return hex.EncodeToString(h.Sum(nil))[:16]
}