// Package atlas builds the CAD Atlas data model, deriving parts from real
// sources (the repo's own CI workflow, infra manifests, the live cluster)
// so the visualization can't drift from reality.
package atlas

import (
	"fmt"

	"gopkg.in/yaml.v3"
)

// JobsFromWorkflow extracts the job names, in document order, from a Gitea
// Actions / GitHub Actions workflow YAML. Used to generate the CI/CD stage of
// the atlas from the pipeline that actually runs, rather than hand-authoring it.
func JobsFromWorkflow(workflow []byte) ([]string, error) {
	var doc yaml.Node
	if err := yaml.Unmarshal(workflow, &doc); err != nil {
		return nil, fmt.Errorf("parse workflow: %w", err)
	}
	if len(doc.Content) == 0 || doc.Content[0].Kind != yaml.MappingNode {
		return nil, fmt.Errorf("workflow: expected a top-level mapping")
	}
	jobs := mappingValue(doc.Content[0], "jobs")
	if jobs == nil {
		return nil, fmt.Errorf("workflow: no jobs block")
	}
	if jobs.Kind != yaml.MappingNode {
		return nil, fmt.Errorf("workflow: jobs is not a mapping")
	}

	// A mapping node stores keys and values as alternating Content entries;
	// keys are the even indices, in document order.
	names := make([]string, 0, len(jobs.Content)/2)
	for i := 0; i+1 < len(jobs.Content); i += 2 {
		names = append(names, jobs.Content[i].Value)
	}
	return names, nil
}

// mappingValue returns the value node for key in a YAML mapping node, or nil.
func mappingValue(m *yaml.Node, key string) *yaml.Node {
	for i := 0; i+1 < len(m.Content); i += 2 {
		if m.Content[i].Value == key {
			return m.Content[i+1]
		}
	}
	return nil
}