package ckprompt

import (
	"context"
	"errors"
	"fmt"

	"go.maximumdirect.net/ckconfig"
	commandkit "go.maximumdirect.net/commandkit"
	promptkit "go.maximumdirect.net/promptkit"
)

// PreparationRequest carries the configuration selection and seed native request
// supplied to preparation callbacks and builders.
type PreparationRequest struct {
	// Selection identifies the configuration sources used to load the engine.
	Selection ckconfig.Selection
	// Request contains the native seed request populated by command inputs.
	Request promptkit.RunRequest
	// Namespaces selects the native engine view; nil preserves the loader view.
	Namespaces *promptkit.Namespaces
}

// WithRequestPreparation attaches native prepared-request inspection. The
// optional builder may replace the complete seed request before engine loading.
// Preparation may read resources and returns rendered application content; it
// does not call the model or retain an execution handle.
func WithRequestPreparation[I, S any](
	suite Suite[I, S],
	load func(context.Context, ckconfig.Selection, I, S) (*promptkit.Engine, error),
	build func(context.Context, PreparationRequest, I, S) (promptkit.RunRequest, error),
) Suite[I, S] {
	if load == nil {
		issues := append([]error(nil), suite.issues...)
		suite.issues = append(issues, errors.New("PromptKit engine loader is nil"))
		return suite
	}
	suite.PrepareRequest = func(ctx context.Context, request PreparationRequest, input I, state S) (commandkit.Acquired[*promptkit.PreparedRun], error) {
		if err := promptKitContextError(ctx); err != nil {
			return commandkit.Acquired[*promptkit.PreparedRun]{}, fmt.Errorf("PromptKit request preparation before building: %w", err)
		}
		concrete := request.Request
		if build != nil {
			built, err := build(ctx, request, input, state)
			if err != nil {
				return commandkit.Acquired[*promptkit.PreparedRun]{}, err
			}
			concrete = built
		}
		if err := promptKitContextError(ctx); err != nil {
			return commandkit.Acquired[*promptkit.PreparedRun]{}, fmt.Errorf("PromptKit request preparation after building: %w", err)
		}
		engine, _, messages, err := loadPromptKitEngine(ctx, request.Selection, input, state, "", load)
		if err != nil {
			return commandkit.Acquired[*promptkit.PreparedRun]{Diagnostics: messages.diagnostics, Explanation: messages.explanation}, err
		}
		if err := promptKitContextError(ctx); err != nil {
			return commandkit.Acquired[*promptkit.PreparedRun]{Diagnostics: messages.diagnostics, Explanation: messages.explanation}, fmt.Errorf("PromptKit request preparation before native preparation: %w", err)
		}
		engine, err = namespacedEngine(engine, request.Namespaces)
		if err != nil {
			messages = messages.withOperationError(err)
			return commandkit.Acquired[*promptkit.PreparedRun]{Diagnostics: messages.diagnostics, Explanation: messages.explanation}, err
		}
		prepared, err := engine.Prepare(ctx, concrete)
		messages = messages.withOperationError(err)
		return commandkit.Acquired[*promptkit.PreparedRun]{Value: prepared, Diagnostics: messages.diagnostics, Explanation: messages.explanation}, err
	}
	return suite
}

func newPreparationCommand[I, S any](suite Suite[I, S]) commandkit.Command {
	spec := newConcreteRequestSpec(suite)
	spec.Name = "prepared"
	spec.Summary = "Show a prepared PromptKit request without calling the model."
	spec.Description = "Prepares the request using resource I/O and reports rendered application content without calling the model."
	spec.Run = func(invocation commandkit.Invocation, input *concreteRequestInput[I]) commandkit.Outcome {
		return runRequestPreparation(invocation, suite, input)
	}
	return commandkit.NewCommand(spec)
}

func runRequestPreparation[I, S any](invocation commandkit.Invocation, suite Suite[I, S], input *concreteRequestInput[I]) commandkit.Outcome {
	if err := promptKitContextError(invocation.Context); err != nil {
		return definitionFailure("PromptKit request preparation was canceled.", commandkit.Explanation{}, err)
	}
	var state S
	if suite.NewState != nil {
		state = suite.NewState()
	}
	if err := promptKitContextError(invocation.Context); err != nil {
		return definitionFailure("PromptKit request preparation was canceled.", commandkit.Explanation{}, err)
	}
	request := PreparationRequest{Selection: input.request.Selection, Request: input.request.Request, Namespaces: input.request.Namespaces}
	acquired, err := suite.PrepareRequest(invocation.Context, request, input.selected, state)
	queuePromptDiagnostics(invocation.Reporter(), acquired.Diagnostics)
	if err != nil {
		return definitionFailure(fmt.Sprintf("Unable to prepare the PromptKit request for prompt %q.", input.promptID), acquired.Explanation, err)
	}
	if err := promptKitContextError(invocation.Context); err != nil {
		return definitionFailure(fmt.Sprintf("Preparation of the PromptKit request for prompt %q was canceled.", input.promptID), acquired.Explanation, err)
	}
	_ = invocation.Reporter().Report(commandkit.Report{Value: acquired.Value})
	return commandkit.Success()
}