package selfcompose

import (
	"context"
	"strings"
)

// KeptBuildOf is the node that keeps the build a module is wanted at, and its fingerprint, for the artifact store's
// holder (design 47 G section 271, 526, A-50): the want's `kept-on` and nothing else names it, the builder's builds being
// no read of the node-engine's (section 421). kept is false when the module has no want, its want names no keeping node,
// or its `parts` do not name the digest ("sha256:" and 64 hex digits, or bare): the artifact is then fetched from the store.
func (c *Composer) KeptBuildOf(_ context.Context, module, digest string) (node, fp string, kept bool, err error) {
	c.mu.Lock()
	w, ok := c.wants[module]
	c.mu.Unlock()
	if !ok || w.Fp == "" || w.KeptOn == "" {
		return "", "", false, nil
	}
	if len(w.Parts) > 0 {
		named := false
		for _, d := range w.Parts {
			if strings.TrimPrefix(d, "sha256:") == strings.TrimPrefix(digest, "sha256:") {
				named = true
			}
		}
		if !named {
			return "", "", false, nil
		}
	}
	return w.KeptOn, w.Fp, true, nil
}