package pool

import (
	"crypto/sha256"
	"fmt"
	"sort"
	"strings"

	"github.com/indifferentketchup/llama-sidecar/internal/validator"
)

// Hash computes a deterministic hash for a (modelID, flags) pair.
// Flag order does not affect the result.
func Hash(modelID string, flags []string) string {
	type pair struct {
		key, val string
	}

	var pairs []pair
	i := 0
	for i < len(flags) {
		tok := flags[i]
		key := validator.FlagName(tok)
		if key == "" {
			i++
			continue
		}
		if idx := strings.IndexByte(tok, '='); idx >= 0 {
			pairs = append(pairs, pair{key: tok[:idx], val: tok[idx+1:]})
			i++
		} else if i+1 < len(flags) && validator.FlagName(flags[i+1]) == "" {
			pairs = append(pairs, pair{key: key, val: flags[i+1]})
			i += 2
		} else {
			pairs = append(pairs, pair{key: key, val: ""})
			i++
		}
	}

	sort.Slice(pairs, func(a, b int) bool {
		return pairs[a].key < pairs[b].key
	})

	var parts []string
	for _, p := range pairs {
		parts = append(parts, p.key+"\x1f"+p.val)
	}
	serialized := strings.Join(parts, "\x1e")
	input := modelID + "\x1d" + serialized

	sum := sha256.Sum256([]byte(input))
	return fmt.Sprintf("%x", sum[:8])
}