package spells

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"mime"
	"strings"

	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
	npccodec "gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/codec/npcs"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/npcs/diagnostics"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/npcs/identity"
)

const (
	NPCRegistryReferenceSlot = "npcs"
	NPCRegistryMaxBytes      = 1048576
)

type npcRegistryPromptInput struct {
	input  contracts.LLMInputMaterial
	digest string
	count  int
	bound  bool
}

func resolveNPCRegistry(references contracts.ReferenceSet) (npcRegistryPromptInput, error) {
	slot, ok := references.Slots[NPCRegistryReferenceSlot]
	if !ok {
		return npcRegistryPromptInput{
			input: contracts.NewLLMInputMaterial(
				NPCRegistryReferenceSlot,
				"application/json",
				[]byte(`{"npcs":[]}`),
				"",
				"",
			),
		}, nil
	}
	if len(slot.Items) != 1 {
		return npcRegistryPromptInput{}, fmt.Errorf("reference slot %q must contain exactly one item", NPCRegistryReferenceSlot)
	}

	item := slot.Items[0]
	mediaType, _, err := mime.ParseMediaType(item.MediaType)
	if err != nil {
		return npcRegistryPromptInput{}, fmt.Errorf("reference slot %q item media type %q is invalid: %w", NPCRegistryReferenceSlot, item.MediaType, err)
	}
	if !strings.EqualFold(mediaType, "application/json") {
		return npcRegistryPromptInput{}, fmt.Errorf("reference slot %q item media type %q must be application/json", NPCRegistryReferenceSlot, item.MediaType)
	}
	if len(item.Content) > NPCRegistryMaxBytes {
		return npcRegistryPromptInput{}, fmt.Errorf("reference slot %q item is %d bytes, limit %d", NPCRegistryReferenceSlot, len(item.Content), NPCRegistryMaxBytes)
	}

	codec := npccodec.New()
	value, err := codec.Decode(item.Content)
	if err != nil {
		return npcRegistryPromptInput{}, fmt.Errorf("decode NPC registry: invalid approved NPC JSON")
	}
	if issues := identity.ValidateList(value); len(issues) > 0 {
		return npcRegistryPromptInput{}, fmt.Errorf("%s", formatNPCIdentityIssues(issues))
	}
	content, err := codec.Encode(value)
	if err != nil {
		return npcRegistryPromptInput{}, fmt.Errorf("encode canonical NPC registry: approved NPC value could not be encoded")
	}

	digest := semanticNPCRegistryDigest(content)
	return npcRegistryPromptInput{
		input:  contracts.NewLLMInputMaterial(NPCRegistryReferenceSlot, "application/json", content, digest, ""),
		digest: digest,
		count:  len(value.NPCs),
		bound:  true,
	}, nil
}

func semanticNPCRegistryDigest(content []byte) string {
	sum := sha256.Sum256(content)
	return "sha256:" + hex.EncodeToString(sum[:])
}

func formatNPCIdentityIssues(issues []identity.Issue) string {
	parts := make([]string, len(issues))
	for index, issue := range issues {
		location := fmt.Sprintf("record %d", issue.RecordIndex)
		if issue.AliasIndex >= 0 {
			location += fmt.Sprintf(" alias %d", issue.AliasIndex)
		}
		parts[index] = fmt.Sprintf("%s at %s", issue.Code, location)
	}
	return diagnostics.Aggregate("validate NPC registry identity", parts)
}