package prediction

import (
	"crypto/rand"
	"encoding/json"
	"fmt"
	"math/big"
)

func BuildPrompt(workflowJSON string, binding InputBinding, input map[string]any) (map[string]any, error) {
	var workflow map[string]any
	if err := json.Unmarshal([]byte(workflowJSON), &workflow); err != nil {
		return nil, fmt.Errorf("invalid workflow: %w", err)
	}
	prompt := deepCopyMap(workflow)
	for name, target := range binding {
		if target == nil || target.Node == "" || target.Field == "" {
			continue
		}
		val, ok := input[name]
		if !ok {
			continue
		}
		if name == "seed" {
			if iv, ok := val.(int); ok && iv < 0 {
				n, _ := rand.Int(rand.Reader, big.NewInt(1<<31-1))
				val = int(n.Int64())
			}
		}
		node, ok := prompt[target.Node].(map[string]any)
		if !ok {
			return nil, fmt.Errorf("node %s not found", target.Node)
		}
		inputs, ok := node["inputs"].(map[string]any)
		if !ok {
			return nil, fmt.Errorf("node %s inputs missing", target.Node)
		}
		inputs[target.Field] = val
	}
	return prompt, nil
}

func deepCopyMap(src map[string]any) map[string]any {
	b, _ := json.Marshal(src)
	var dst map[string]any
	_ = json.Unmarshal(b, &dst)
	return dst
}