package modules

import (
	"context"
	"fmt"
	"strings"

	"gitea.maximumdirect.net/eric/audita/internal/core/config"
	"gitea.maximumdirect.net/eric/audita/internal/core/schema"
	"gitea.maximumdirect.net/eric/audita/internal/framework/contracts"
)

const (
	ModuleKeyGlossary   = "glossary"
	ModuleKeyHomophones = "homophones"
	ModuleKeySpokenWord = "spoken_word"
	ModuleKeyGrammar    = "grammar"
)

const (
	ReasonUnsupportedModule   = "unsupported_module"
	ReasonUnimplementedModule = "unimplemented_module"
)

var knownModuleKeys = map[string]struct{}{
	ModuleKeyGlossary:   {},
	ModuleKeyHomophones: {},
	ModuleKeySpokenWord: {},
	ModuleKeyGrammar:    {},
}

// IsKnownModuleKey reports whether a module key is recognized by the production
// registry scaffold.
func IsKnownModuleKey(key string) bool {
	_, ok := knownModuleKeys[strings.TrimSpace(key)]
	return ok
}

// Dependencies holds explicit constructor dependencies for module creation.
type Dependencies struct {
	Config                 *config.Config
	Glossary               *schema.Glossary
	ProposalLLMClient      contracts.StructuredLLMClient
	ProposalLLMScheduler   contracts.LLMScheduler
	ValidationLLMClient    contracts.StructuredLLMClient
	ValidationLLMScheduler contracts.LLMScheduler
	DiagnosticsDir         string
}

// ConstructRequest is one module-construction request.
type ConstructRequest struct {
	RunSpec contracts.ModuleRunSpec
	Dependencies
}

// Constructor builds one module instance from a run spec and explicit deps.
type Constructor func(ctx context.Context, req ConstructRequest) (contracts.TranscriptModule, error)

// Factory resolves configured module specs into module instances.
type Factory struct {
	deps         Dependencies
	constructors map[string]Constructor
}

// NewFactory creates a production registry scaffold with known module keys but
// no real module constructors registered yet.
func NewFactory(deps Dependencies) *Factory {
	return &Factory{
		deps:         deps,
		constructors: make(map[string]Constructor, len(knownModuleKeys)),
	}
}

// RegisterConstructor registers a constructor for a known module key.
func (f *Factory) RegisterConstructor(moduleKey string, constructor Constructor) error {
	if f == nil {
		return fmt.Errorf("module factory is nil")
	}
	key := strings.TrimSpace(moduleKey)
	if !IsKnownModuleKey(key) {
		return &UnsupportedModuleError{ModuleKey: key}
	}
	if constructor == nil {
		return fmt.Errorf("constructor for module %q must not be nil", key)
	}
	f.constructors[key] = constructor
	return nil
}

// ModuleForSpec resolves one configured run spec into a module instance.
func (f *Factory) ModuleForSpec(spec contracts.ModuleRunSpec) (contracts.TranscriptModule, error) {
	if f == nil {
		return nil, fmt.Errorf("module factory is nil")
	}

	key := strings.TrimSpace(spec.ModuleKey)
	if !IsKnownModuleKey(key) {
		return nil, &UnsupportedModuleError{ModuleKey: key}
	}

	constructor, ok := f.constructors[key]
	if !ok || constructor == nil {
		return nil, &UnimplementedModuleError{ModuleKey: key}
	}

	module, err := constructor(context.Background(), ConstructRequest{
		RunSpec: spec,
		Dependencies: Dependencies{
			Config:                 f.deps.Config,
			Glossary:               f.deps.Glossary,
			ProposalLLMClient:      f.deps.ProposalLLMClient,
			ProposalLLMScheduler:   f.deps.ProposalLLMScheduler,
			ValidationLLMClient:    f.deps.ValidationLLMClient,
			ValidationLLMScheduler: f.deps.ValidationLLMScheduler,
			DiagnosticsDir:         f.deps.DiagnosticsDir,
		},
	})
	if err != nil {
		return nil, fmt.Errorf("construct module %q: %w", spec.InstanceName, err)
	}
	if module == nil {
		return nil, fmt.Errorf("constructor for module %q returned nil module", key)
	}
	return module, nil
}

// UnsupportedModuleError indicates a configured module key is unknown.
type UnsupportedModuleError struct {
	ModuleKey string
}

func (e *UnsupportedModuleError) Error() string {
	return fmt.Sprintf("unsupported module key %q", strings.TrimSpace(e.ModuleKey))
}

// ReasonCode returns a stable reason code suitable for reporting.
func (e *UnsupportedModuleError) ReasonCode() string {
	return ReasonUnsupportedModule
}

// UnimplementedModuleError indicates a known module key without constructor.
type UnimplementedModuleError struct {
	ModuleKey string
}

func (e *UnimplementedModuleError) Error() string {
	return fmt.Sprintf("module %q is recognized but not implemented", strings.TrimSpace(e.ModuleKey))
}

// ReasonCode returns a stable reason code suitable for reporting.
func (e *UnimplementedModuleError) ReasonCode() string {
	return ReasonUnimplementedModule
}