package atlas

import (
	"bytes"
	"encoding/json"
	"fmt"
)

// GenerateKeys names the live sources a stage draws nodes from. A stage grew
// past one source once stuck-badges landed alongside the existing overlays, so
// this accepts either spelling in atlas.json:
//
//	"generate": "ci-jobs"
//	"generate": ["stuck-badges", "gitea-repos"]
//
// The bare string is kept rather than migrated: most stages have exactly one
// source, and a one-element list reads worse for no benefit.
type GenerateKeys []string

// Has reports whether the stage draws from the named source. The empty key
// never matches, so a stage with no `generate` is inert.
func (g GenerateKeys) Has(key string) bool {
	if key == "" {
		return false
	}
	for _, k := range g {
		if k == key {
			return true
		}
	}
	return false
}

func (g *GenerateKeys) UnmarshalJSON(b []byte) error {
	b = bytes.TrimSpace(b)
	if len(b) == 0 || string(b) == "null" {
		*g = nil
		return nil
	}
	if b[0] == '"' {
		var one string
		if err := json.Unmarshal(b, &one); err != nil {
			return fmt.Errorf("parse generate: %w", err)
		}
		*g = GenerateKeys{one}
		return nil
	}
	var many []string
	if err := json.Unmarshal(b, &many); err != nil {
		return fmt.Errorf("parse generate: %w", err)
	}
	*g = many
	return nil
}

// MarshalJSON writes a lone key back as a bare string, so a round-trip through
// the API does not rewrite every authored stage into list form.
func (g GenerateKeys) MarshalJSON() ([]byte, error) {
	if len(g) == 1 {
		return json.Marshal(g[0])
	}
	return json.Marshal([]string(g))
}