// Package stubprovider provides the deterministic local provider used by Mail
// Service tests and local bootstrap flows.
package stubprovider

import (
	"context"
	"errors"
	"fmt"
	"sync"

	"galaxy/mail/internal/domain/common"
	deliverydomain "galaxy/mail/internal/domain/delivery"
	"galaxy/mail/internal/ports"
)

const providerName = "stub"

// ScriptedOutcome stores one queued stub-provider result consumed by the next
// Send call.
type ScriptedOutcome struct {
	// Classification stores the stable provider result classification.
	Classification ports.Classification

	// Script stores the optional stable script label included in the redacted
	// provider summary.
	Script string

	// Details stores optional in-memory-only diagnostic fields associated with
	// the scripted result.
	Details map[string]string
}

// Validate reports whether outcome contains one supported queued stub result.
func (outcome ScriptedOutcome) Validate() error {
	if !outcome.Classification.IsKnown() {
		return fmt.Errorf("stub scripted classification %q is unsupported", outcome.Classification)
	}
	if outcome.Script != "" {
		if _, err := ports.BuildSafeSummary(ports.SummaryFields{
			Provider: providerName,
			Result:   string(outcome.Classification),
			Script:   outcome.Script,
		}); err != nil {
			return fmt.Errorf("stub scripted outcome: %w", err)
		}
	}
	for key, value := range outcome.Details {
		result := ports.Result{
			Classification: outcome.Classification,
			Summary:        "provider=stub result=accepted",
			Details: map[string]string{
				key: value,
			},
		}
		if err := result.Validate(); err != nil {
			return fmt.Errorf("stub scripted details: %w", err)
		}
	}

	return nil
}

// Provider stores one deterministic in-memory provider implementation.
type Provider struct {
	mu     sync.Mutex
	queue  []ScriptedOutcome
	inputs []ports.Message
	closed bool
}

// New constructs the deterministic stub provider.
func New(initial ...ScriptedOutcome) (*Provider, error) {
	provider := &Provider{}
	if err := provider.Enqueue(initial...); err != nil {
		return nil, fmt.Errorf("new stub provider: %w", err)
	}

	return provider, nil
}

// Send records message and returns the next scripted outcome, or a stable
// accepted outcome when no script remains.
func (provider *Provider) Send(ctx context.Context, message ports.Message) (ports.Result, error) {
	switch {
	case ctx == nil:
		return ports.Result{}, errors.New("send with stub provider: nil context")
	case provider == nil:
		return ports.Result{}, errors.New("send with stub provider: nil provider")
	}
	if err := message.Validate(); err != nil {
		return ports.Result{}, fmt.Errorf("send with stub provider: %w", err)
	}

	provider.mu.Lock()
	defer provider.mu.Unlock()

	if provider.closed {
		return ports.Result{}, errors.New("send with stub provider: provider is closed")
	}

	provider.inputs = append(provider.inputs, cloneMessage(message))

	if len(provider.queue) == 0 {
		return scriptedResult(ScriptedOutcome{
			Classification: ports.ClassificationAccepted,
		})
	}

	next := provider.queue[0]
	provider.queue = provider.queue[1:]
	return scriptedResult(next)
}

// Close marks the provider as closed. Future Send calls fail fast.
func (provider *Provider) Close() error {
	if provider == nil {
		return nil
	}

	provider.mu.Lock()
	defer provider.mu.Unlock()
	provider.closed = true
	return nil
}

// Enqueue appends scripted outcomes to the stub queue.
func (provider *Provider) Enqueue(outcomes ...ScriptedOutcome) error {
	if provider == nil {
		return errors.New("enqueue stub provider outcomes: nil provider")
	}

	provider.mu.Lock()
	defer provider.mu.Unlock()

	for index, outcome := range outcomes {
		if err := outcome.Validate(); err != nil {
			return fmt.Errorf("enqueue stub provider outcomes[%d]: %w", index, err)
		}
		provider.queue = append(provider.queue, ScriptedOutcome{
			Classification: outcome.Classification,
			Script:         outcome.Script,
			Details:        ports.CloneDetails(outcome.Details),
		})
	}

	return nil
}

// Inputs returns a detached snapshot of the accepted Send inputs.
func (provider *Provider) Inputs() []ports.Message {
	if provider == nil {
		return nil
	}

	provider.mu.Lock()
	defer provider.mu.Unlock()

	inputs := make([]ports.Message, len(provider.inputs))
	for index, input := range provider.inputs {
		inputs[index] = cloneMessage(input)
	}

	return inputs
}

func scriptedResult(outcome ScriptedOutcome) (ports.Result, error) {
	summary, err := ports.BuildSafeSummary(ports.SummaryFields{
		Provider: providerName,
		Result:   string(outcome.Classification),
		Script:   outcome.Script,
	})
	if err != nil {
		return ports.Result{}, fmt.Errorf("build stub provider summary: %w", err)
	}

	result := ports.Result{
		Classification: outcome.Classification,
		Summary:        summary,
		Details:        ports.CloneDetails(outcome.Details),
	}
	if err := result.Validate(); err != nil {
		return ports.Result{}, fmt.Errorf("build stub provider result: %w", err)
	}

	return result, nil
}

func cloneMessage(message ports.Message) ports.Message {
	cloned := ports.Message{
		Envelope: deliverydomain.Envelope{
			To:      append([]common.Email(nil), message.Envelope.To...),
			Cc:      append([]common.Email(nil), message.Envelope.Cc...),
			Bcc:     append([]common.Email(nil), message.Envelope.Bcc...),
			ReplyTo: append([]common.Email(nil), message.Envelope.ReplyTo...),
		},
		Content: message.Content,
	}
	if len(message.Attachments) > 0 {
		cloned.Attachments = make([]ports.Attachment, len(message.Attachments))
		for index, attachment := range message.Attachments {
			content := make([]byte, len(attachment.Content))
			copy(content, attachment.Content)
			cloned.Attachments[index] = ports.Attachment{
				Metadata: attachment.Metadata,
				Content:  content,
			}
		}
	}

	return cloned
}