// Package engine assembles Promptkit's internal execution components.
package engine

import (
	"context"
	"fmt"
	"net/http"
	"strings"
	"time"

	openrouter "gitea.maximumdirect.net/eric/promptkit-backend-openrouter"
	rakestrawhome "gitea.maximumdirect.net/eric/promptkit-backend-rakestrawhome"
	"gitea.maximumdirect.net/eric/promptkit/internal/artifact"
	"gitea.maximumdirect.net/eric/promptkit/internal/backend"
	"gitea.maximumdirect.net/eric/promptkit/internal/capacity"
	"gitea.maximumdirect.net/eric/promptkit/internal/catalog"
	"gitea.maximumdirect.net/eric/promptkit/internal/defaults"
	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
	"gitea.maximumdirect.net/eric/promptkit/internal/llm"
	"gitea.maximumdirect.net/eric/promptkit/internal/profile"
	"gitea.maximumdirect.net/eric/promptkit/internal/prompt"
	"gitea.maximumdirect.net/eric/promptkit/internal/promptdef"
	"gitea.maximumdirect.net/eric/promptkit/internal/usecase"
	"gitea.maximumdirect.net/eric/promptkit/internal/validate"
)

// Config carries construction settings selected by the public facade.
type Config struct {
	PromptDir  string
	ProfileDir string
	SchemaDir  string
	Timeout    time.Duration
	HTTPClient *http.Client
}

// Options carries collaborators prepared by the public facade during the
// transitional composition split.
type Options struct {
	LLMClient             llm.Client
	ArtifactReader        artifact.Reader
	PromptDefinitions     promptdef.Repository
	Profiles              profile.Repository
	FallbackProfiles      profile.Repository
	MemoryProfiles        profile.Repository
	Backends              []domain.Backend
	Validator             validate.Validator
	PromptSource          bool
	ProfileSource         bool
	FallbackProfileSource bool
	MemorySource          bool
	ValidatorSource       bool
	ArtifactSource        bool
}

// Engine forwards domain operations to the single assembled use-case runner.
type Engine struct {
	runner *usecase.Runner
}

// New assembles an engine from facade-selected configuration and collaborators.
func New(cfg Config, options Options) (*Engine, error) {
	promptDefinitions := options.PromptDefinitions
	if !options.PromptSource {
		if strings.TrimSpace(cfg.PromptDir) == "" {
			return nil, fmt.Errorf("prompt directory is required")
		}
		promptDefinitions = promptdef.NewFilesystemRepository(cfg.PromptDir)
	}

	maintained, err := catalog.Load(
		catalog.Source{Name: "OpenRouter", ExpectedBackendID: backend.OpenRouterID, FS: openrouter.FS(), Root: openrouter.Root},
		catalog.Source{Name: "Rakestrawhome", ExpectedBackendID: backend.RakestrawHomeID, FS: rakestrawhome.FS(), Root: rakestrawhome.Root},
	)
	if err != nil {
		return nil, fmt.Errorf("failed to load maintained catalogs: %w", err)
	}

	profiles := newProfileRepository(cfg.ProfileDir, options, maintained.Profiles)
	registry, err := backend.NewRegistry(maintained.Backends, options.Backends)
	if err != nil {
		return nil, fmt.Errorf("failed to construct backend registry: %w", err)
	}
	manager, err := capacity.NewManager(registry.CapacityPolicies())
	if err != nil {
		return nil, fmt.Errorf("failed to construct backend capacity manager: %w", err)
	}

	validator := options.Validator
	if !options.ValidatorSource {
		schemaDir := cfg.SchemaDir
		if strings.TrimSpace(schemaDir) == "" {
			schemaDir = defaults.SchemaDirDefault
		}
		validator = validate.NewStandardValidator(schemaDir)
	}
	client := options.LLMClient
	if client == nil {
		client, err = llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{Timeout: cfg.Timeout, HTTPClient: cfg.HTTPClient})
		if err != nil {
			return nil, err
		}
	}
	client = capacity.NewClient(manager, client)
	reader := options.ArtifactReader
	if !options.ArtifactSource {
		reader = artifact.NewCompositeReader()
	}

	return &Engine{runner: usecase.NewRunnerWithRepairer(promptDefinitions, profiles, registry, reader, prompt.NewGoRenderer(), client, validator, usecase.NewDefaultOutputRepairer(client), manager)}, nil
}

func newProfileRepository(profileDir string, options Options, maintained profile.Repository) profile.Repository {
	repository := maintained
	if options.FallbackProfileSource {
		repository = profile.NewOverlayRepository(options.FallbackProfiles, repository)
	}
	if options.ProfileSource {
		repository = profile.NewOverlayRepository(options.Profiles, repository)
	} else if strings.TrimSpace(profileDir) != "" {
		repository = profile.NewOverlayRepository(profile.NewFilesystemRepository(profileDir), repository)
	}
	if options.MemorySource {
		repository = profile.NewOverlayRepository(options.MemoryProfiles, repository)
	}
	return profile.NewResolvingRepository(repository)
}

func (e *Engine) InspectPrompt(ctx context.Context, id, version string) (*domain.PromptInspection, error) {
	return e.runner.InspectPrompt(ctx, id, version)
}
func (e *Engine) InspectProfile(ctx context.Context, id string) (*domain.ProfileInspection, error) {
	return e.runner.InspectProfile(ctx, id)
}
func (e *Engine) Prepare(ctx context.Context, request domain.RunRequest) (*domain.PreparedRun, error) {
	return e.runner.Prepare(ctx, request)
}
func (e *Engine) PrepareExecution(ctx context.Context, request domain.RunRequest) (*usecase.PreparedExecution, error) {
	return e.runner.PrepareExecution(ctx, request)
}
func (e *Engine) Run(ctx context.Context, request domain.RunRequest) (*domain.RunResult, error) {
	return e.runner.Run(ctx, request)
}
func (e *Engine) RunPrepared(ctx context.Context, prepared *usecase.PreparedExecution) (*domain.RunResult, error) {
	return e.runner.RunPrepared(ctx, prepared)
}