package profile

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
	"gitea.maximumdirect.net/eric/promptkit/internal/jsonvalue"
)

const maximumProfileChainLength = 32

type resolvingRepository struct {
	source Repository
}

// NewResolvingRepository resolves inherited profile definitions from source.
func NewResolvingRepository(source Repository) Repository {
	return &resolvingRepository{source: source}
}

func (r *resolvingRepository) GetProfile(ctx context.Context, id string) (*domain.ExecutionProfile, error) {
	if r == nil || r.source == nil {
		return nil, fmt.Errorf("%w: profile repository is required", ErrInvalidProfile)
	}
	requestedID := strings.TrimSpace(id)
	if requestedID == "" {
		return nil, fmt.Errorf("%w: profile id is required", ErrInvalidProfile)
	}
	if err := ctx.Err(); err != nil {
		return nil, err
	}

	profile, err := r.source.GetProfile(ctx, requestedID)
	if err != nil {
		return nil, err
	}
	if profile == nil {
		return nil, fmt.Errorf("%w: selected profile %q is nil", ErrInvalidProfile, requestedID)
	}

	chain := []*domain.ExecutionProfile{profile}
	chainIDs := []string{requestedID}
	visited := map[string]struct{}{requestedID: {}}
	current := profile

	for {
		baseID := strings.TrimSpace(current.BaseProfileID)
		if baseID == "" {
			break
		}
		if err := ctx.Err(); err != nil {
			return nil, err
		}
		if _, seen := visited[baseID]; seen {
			return nil, fmt.Errorf("%w: profile inheritance cycle %s", ErrInvalidProfile, joinProfileChain(chainIDs, baseID))
		}
		if len(chain) >= maximumProfileChainLength {
			return nil, fmt.Errorf("%w: profile inheritance chain exceeds %d profiles: %s", ErrInvalidProfile, maximumProfileChainLength, joinProfileChain(chainIDs, baseID))
		}

		base, err := r.source.GetProfile(ctx, baseID)
		if err != nil {
			if errors.Is(err, ErrProfileNotFound) {
				return nil, fmt.Errorf("%w: base profile %q is missing in chain %s", ErrInvalidProfile, baseID, joinProfileChain(chainIDs, baseID))
			}
			return nil, fmt.Errorf("%w: failed to load base profile %q in chain %s: %w", ErrInvalidProfile, baseID, joinProfileChain(chainIDs, baseID), err)
		}
		if base == nil {
			return nil, fmt.Errorf("%w: base profile %q is nil in chain %s", ErrInvalidProfile, baseID, joinProfileChain(chainIDs, baseID))
		}

		chain = append(chain, base)
		chainIDs = append(chainIDs, baseID)
		visited[baseID] = struct{}{}
		current = base
	}

	resolved, err := mergeProfileChain(chain)
	if err != nil {
		return nil, fmt.Errorf("%w: resolved profile chain %s: %w", ErrInvalidProfile, strings.Join(chainIDs, " -> "), err)
	}
	if err := validateResolvedProfile(resolved); err != nil {
		return nil, fmt.Errorf("%w: resolved profile chain %s: %w", ErrInvalidProfile, strings.Join(chainIDs, " -> "), err)
	}
	return resolved, nil
}

func joinProfileChain(chain []string, next string) string {
	return strings.Join(append(append([]string(nil), chain...), next), " -> ")
}

func mergeProfileChain(chain []*domain.ExecutionProfile) (*domain.ExecutionProfile, error) {
	resolved := &domain.ExecutionProfile{ID: chain[0].ID}
	for index := len(chain) - 1; index >= 0; index-- {
		definition := chain[index]
		if strings.TrimSpace(definition.BackendID) != "" {
			resolved.BackendID = definition.BackendID
		}
		if strings.TrimSpace(definition.Endpoint) != "" {
			resolved.Endpoint = definition.Endpoint
		}
		if strings.TrimSpace(definition.Model) != "" {
			resolved.Model = definition.Model
		}
		if definition.Temperature != 0 {
			resolved.Temperature = definition.Temperature
		}
		if definition.MaxTokens != 0 {
			resolved.MaxTokens = definition.MaxTokens
		}
		if definition.TopP != 0 {
			resolved.TopP = definition.TopP
		}
		if definition.TimeoutSeconds != 0 {
			resolved.TimeoutSeconds = definition.TimeoutSeconds
		}
		if strings.TrimSpace(definition.ServiceTier) != "" {
			resolved.ServiceTier = definition.ServiceTier
		}
		if strings.TrimSpace(definition.ReasoningEffort) != "" {
			resolved.ReasoningEffort = definition.ReasoningEffort
		}
		if strings.TrimSpace(definition.APIKeyEnv) != "" {
			resolved.APIKeyEnv = definition.APIKeyEnv
		}
		resolved.APIKeyRequired = resolved.APIKeyRequired || definition.APIKeyRequired
		if len(definition.ExtraParams) != 0 {
			extraParams, err := jsonvalue.CopyMap(definition.ExtraParams)
			if err != nil {
				return nil, err
			}
			resolved.ExtraParams = extraParams
		}
	}
	resolved.ID = chain[0].ID
	resolved.BaseProfileID = ""
	return resolved, nil
}

func validateResolvedProfile(profile *domain.ExecutionProfile) error {
	if profile == nil {
		return errors.New("resolved profile is required")
	}
	profile.BaseProfileID = ""
	return NormalizeAndValidateDefinition(profile)
}