package ckprompt

import (
	"context"
	"errors"
	"fmt"
	"io"
	"strconv"

	commandkit "gitea.maximumdirect.net/eric/CommandKit"
	"gitea.maximumdirect.net/eric/CommandKit/integrations/ckconfig"
	configkit "gitea.maximumdirect.net/eric/ConfigKit"
	promptkit "gitea.maximumdirect.net/eric/promptkit"
)

// PromptRequest selects one named prompt for inspection.
type PromptRequest struct {
	// Selection carries the configuration and overlay values supplied to the command.
	Selection ckconfig.Selection
	// ID is the selected named prompt.
	ID string
	// Version carries the explicitly supplied prompt version, if present.
	Version commandkit.Supplied[string]
}

// ProfileRequest selects one named profile for inspection.
type ProfileRequest struct {
	// Selection carries the configuration and overlay values supplied to the command.
	Selection ckconfig.Selection
	// ID is the selected named profile.
	ID string
}

// RequirementsRequest selects a prompt context for native requirements
// inspection.
type RequirementsRequest struct {
	// Selection carries the configuration and overlay values supplied to the command.
	Selection ckconfig.Selection
	// Inspection forwards PromptKit's native prompt, version, profile, variable,
	// and session discovery context. Optional version, profile, and session
	// strings retain PromptKit's empty-value semantics.
	Inspection promptkit.RequirementInspectionRequest
}

// Suite describes application-owned input, shared state, and optional catalog,
// named inspection, and requirements inspection capabilities. Its private
// issues retain adapter construction failures.
// Factory results and callback effects remain caller-owned: Command does not
// deep-copy arbitrary objects or repair aliases returned by factories.
// A reached operation prepares one input, applies its captured selectors, and
// checks the input before creating state and calling the selected provider.
// Factories are not invoked during construction, installation, help, or version,
// and need not run after failure.
type Suite[I, S any] struct {
	// NewInput is called once when definition, requirements, or catalog input
	// preparation is reached, before applying selectors and calling CheckInput.
	// If nil, input is the zero value of I, including nil for pointer types.
	NewInput func() I
	// NewState is called once when an inspection or catalog callback is reached,
	// after input checks pass. If nil, state is the zero value of S, including
	// nil for pointer types.
	NewState func() S
	// Selectors declares the original typed flags accepted by definition,
	// requirements, and catalog commands.
	Selectors []commandkit.Flag[I]
	// CheckInput validates selected definition, requirements, or catalog input
	// before state creation.
	CheckInput func(ckconfig.Selection, I) error
	// InspectPrompt inspects the selected prompt after input and state preparation.
	InspectPrompt func(context.Context, PromptRequest, I, S) (commandkit.Acquired[*promptkit.PromptInspection], error)
	// InspectProfile inspects the selected profile after input and state preparation.
	InspectProfile func(context.Context, ProfileRequest, I, S) (commandkit.Acquired[*promptkit.ProfileInspection], error)
	// InspectRequirements inspects native PromptKit requirements after input and
	// state preparation. It is optional; a nil callback omits the requirements
	// command without disabling other capabilities.
	InspectRequirements func(context.Context, RequirementsRequest, I, S) (commandkit.Acquired[*promptkit.RequirementInspection], error)
	// ListPrompts lists prompt identities after input and state preparation.
	// It is optional; a nil callback does not install a prompt catalog command.
	ListPrompts func(context.Context, ckconfig.Selection, I, S) (commandkit.Acquired[[]promptkit.PromptIdentity], error)
	// ListProfiles lists profile IDs after input and state preparation.
	// It is optional; a nil callback does not install a profile catalog command.
	ListProfiles func(context.Context, ckconfig.Selection, I, S) (commandkit.Acquired[[]string], error)

	issues []error
}

type engineLoader[I, S any] func(context.Context, ckconfig.Selection, I, S) (*promptkit.Engine, error)

// ConfigScope adapts PromptKit's captured configuration inspection to the
// standard configuration commands, including native comparison when the scope
// declares Diff. The loader is not called during declaration construction or
// installation; it is called only when a config operation selects the
// promptkit scope, with that operation's input and shared state. PromptKit
// diagnostics and supported error identity are returned through ckconfig's
// acquisition and comparison contracts.
func ConfigScope[I, S any](load func(context.Context, ckconfig.Selection, I, S) (*promptkit.Engine, error)) ckconfig.Scope[I, S] {
	scope := ckconfig.Scope[I, S]{
		Name:       "promptkit",
		Summary:    "PromptKit engine configuration.",
		Operations: []ckconfig.Operation{ckconfig.Validate, ckconfig.Show, ckconfig.Sources, ckconfig.Explain, ckconfig.Diff},
	}
	if load == nil {
		return ckconfig.WithScopeError(scope, errors.New("PromptKit configuration loader is nil"))
	}

	scope.Acquire = func(ctx context.Context, request ckconfig.Request, input I, state S) (commandkit.Acquired[ckconfig.View], error) {
		_, inspection, diagnostics, err := loadPromptKitEngine(ctx, request.Selection, input, state, "", load)
		if err != nil {
			return commandkit.Acquired[ckconfig.View]{Diagnostics: diagnostics}, err
		}
		return commandkit.Acquired[ckconfig.View]{
			Value: ckconfig.View{
				Effective:   inspection,
				Sources:     inspection,
				Explanation: inspection,
			},
			Diagnostics: diagnostics,
		}, nil
	}
	scope.Compare = func(ctx context.Context, request ckconfig.ComparisonRequest[I], state S) (commandkit.Acquired[[]configkit.Difference], error) {
		if err := promptKitContextError(ctx); err != nil {
			return commandkit.Acquired[[]configkit.Difference]{}, fmt.Errorf("PromptKit scope %q comparison before left load: %w", scope.Name, err)
		}

		_, leftInspection, leftDiagnostics, err := loadPromptKitEngine(ctx, request.Left.Selection, request.Left.Input, state, "left", load)
		diagnostics := append([]commandkit.Diagnostic(nil), leftDiagnostics...)
		if err != nil {
			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q left comparison load: %w", scope.Name, err)
		}

		if err := promptKitContextError(ctx); err != nil {
			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q comparison after left load: %w", scope.Name, err)
		}

		_, rightInspection, rightDiagnostics, err := loadPromptKitEngine(ctx, request.Right.Selection, request.Right.Input, state, "right", load)
		diagnostics = append(diagnostics, rightDiagnostics...)
		if err != nil {
			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q right comparison load: %w", scope.Name, err)
		}

		if err := promptKitContextError(ctx); err != nil {
			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q comparison before native diff: %w", scope.Name, err)
		}

		differences, err := leftInspection.Diff(rightInspection)
		if err != nil {
			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q native configuration diff: %w", scope.Name, err)
		}
		return commandkit.Acquired[[]configkit.Difference]{Value: differences, Diagnostics: diagnostics}, nil
	}
	return scope
}

func promptKitContextError(ctx context.Context) error {
	if ctx == nil {
		return nil
	}
	return ctx.Err()
}

// FromEngine supplies prompt and profile catalog callbacks, named inspection
// callbacks, and a requirements inspection callback backed by a PromptKit engine
// loader. The requirements callback forwards RequirementsRequest.Inspection to
// Engine.InspectRequirements. FromEngine does not call the loader during
// construction. Each selected operation passes its context, supplied
// selection, initialized input, and shared invocation state to the loader before
// calling PromptKit's public listing or inspection method. Applications can
// narrow, wrap, or replace these callbacks before Command captures them. A nil
// loader is retained as an adapter issue.
func FromEngine[I, S any](load func(context.Context, ckconfig.Selection, I, S) (*promptkit.Engine, error)) Suite[I, S] {
	if load == nil {
		return Suite[I, S]{issues: []error{errors.New("PromptKit engine loader is nil")}}
	}

	return Suite[I, S]{
		ListPrompts: func(ctx context.Context, selection ckconfig.Selection, input I, state S) (commandkit.Acquired[[]promptkit.PromptIdentity], error) {
			engine, _, diagnostics, err := loadPromptKitEngine(ctx, selection, input, state, "", load)
			if err != nil {
				return commandkit.Acquired[[]promptkit.PromptIdentity]{Diagnostics: diagnostics}, err
			}
			prompts, err := engine.ListPrompts(ctx)
			return commandkit.Acquired[[]promptkit.PromptIdentity]{Value: prompts, Diagnostics: diagnostics}, err
		},
		ListProfiles: func(ctx context.Context, selection ckconfig.Selection, input I, state S) (commandkit.Acquired[[]string], error) {
			engine, _, diagnostics, err := loadPromptKitEngine(ctx, selection, input, state, "", load)
			if err != nil {
				return commandkit.Acquired[[]string]{Diagnostics: diagnostics}, err
			}
			profiles, err := engine.ListProfiles(ctx)
			return commandkit.Acquired[[]string]{Value: profiles, Diagnostics: diagnostics}, err
		},
		InspectPrompt: func(ctx context.Context, request PromptRequest, input I, state S) (commandkit.Acquired[*promptkit.PromptInspection], error) {
			engine, _, diagnostics, err := loadPromptKitEngine(ctx, request.Selection, input, state, "", load)
			if err != nil {
				return commandkit.Acquired[*promptkit.PromptInspection]{Diagnostics: diagnostics}, err
			}
			inspection, err := engine.InspectPrompt(ctx, request.ID, request.Version.Value)
			return commandkit.Acquired[*promptkit.PromptInspection]{Value: inspection, Diagnostics: diagnostics}, err
		},
		InspectProfile: func(ctx context.Context, request ProfileRequest, input I, state S) (commandkit.Acquired[*promptkit.ProfileInspection], error) {
			engine, _, diagnostics, err := loadPromptKitEngine(ctx, request.Selection, input, state, "", load)
			if err != nil {
				return commandkit.Acquired[*promptkit.ProfileInspection]{Diagnostics: diagnostics}, err
			}
			inspection, err := engine.InspectProfile(ctx, request.ID)
			return commandkit.Acquired[*promptkit.ProfileInspection]{Value: inspection, Diagnostics: diagnostics}, err
		},
		InspectRequirements: func(ctx context.Context, request RequirementsRequest, input I, state S) (commandkit.Acquired[*promptkit.RequirementInspection], error) {
			engine, _, diagnostics, err := loadPromptKitEngine(ctx, request.Selection, input, state, "", load)
			if err != nil {
				return commandkit.Acquired[*promptkit.RequirementInspection]{Diagnostics: diagnostics}, err
			}
			inspection, err := engine.InspectRequirements(ctx, request.Inspection)
			return commandkit.Acquired[*promptkit.RequirementInspection]{Value: inspection, Diagnostics: diagnostics}, err
		},
	}
}

func loadPromptKitEngine[I, S any](
	ctx context.Context,
	selection ckconfig.Selection,
	input I,
	state S,
	side string,
	load engineLoader[I, S],
) (*promptkit.Engine, promptkit.ConfigurationInspection, []commandkit.Diagnostic, error) {
	engine, err := load(ctx, selection, input, state)
	if err != nil {
		var loadErr *configkit.LoadError
		if errors.As(err, &loadErr) {
			return nil, promptkit.ConfigurationInspection{}, promptKitDiagnostics("promptkit", side, loadErr.Sources(), loadErr.Diagnostics()), err
		}
		return nil, promptkit.ConfigurationInspection{}, nil, err
	}
	if engine == nil {
		return nil, promptkit.ConfigurationInspection{}, nil, errors.New("PromptKit configuration loader returned a nil engine")
	}
	inspection, err := engine.InspectConfiguration()
	if err != nil {
		return nil, promptkit.ConfigurationInspection{}, nil, err
	}
	diagnostics := promptKitDiagnostics("promptkit", side, inspection.Sources(), inspection.Diagnostics())
	if ctx != nil {
		if err := ctx.Err(); err != nil {
			return nil, promptkit.ConfigurationInspection{}, diagnostics, err
		}
	}
	return engine, inspection, diagnostics, nil
}

func promptKitDiagnostics(scope, side string, sources []configkit.SourceInfo, records []configkit.Diagnostic) []commandkit.Diagnostic {
	if len(records) == 0 {
		return nil
	}
	severity := commandkit.SeverityWarning
	for _, record := range records {
		if record.Severity == configkit.SeverityError {
			severity = commandkit.SeverityError
			break
		}
	}
	// Snapshot provider-owned slices before deferring their report to invocation.
	sources = append([]configkit.SourceInfo(nil), sources...)
	records = append([]configkit.Diagnostic(nil), records...)
	for index := range records {
		if records[index].Primary != nil {
			primary := *records[index].Primary
			records[index].Primary = &primary
		}
		records[index].Related = append([]configkit.Location(nil), records[index].Related...)
	}
	return []commandkit.Diagnostic{{
		Severity: severity,
		Write: func(writer io.Writer) error {
			heading := "Configuration scope " + strconv.Quote(scope)
			if side != "" {
				heading += " (" + side + ")"
			}
			if _, err := fmt.Fprintf(writer, "%s:\n", heading); err != nil {
				return err
			}
			if len(sources) > 0 {
				if _, err := io.WriteString(writer, "Source IDs:\n"); err != nil {
					return err
				}
				for _, source := range sources {
					if _, err := fmt.Fprintf(writer, "  %s: label=%s, path=%s\n", strconv.Quote(source.ID), strconv.Quote(source.Label), strconv.Quote(source.Path)); err != nil {
						return err
					}
				}
			}
			return configkit.WriteDiagnostics(writer, records)
		},
	}}
}