package artifacts

import (
	"context"
	"errors"
	"fmt"
	"os"
	"strings"

	"gitea.maximumdirect.net/eric/narratio/internal/adapters/storage"
	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
)

var (
	ErrCurrentRunPointerMissing = errors.New("current run pointer missing")
	ErrCurrentManifestMissing   = errors.New("current manifest missing")
)

type CurrentRunPointerMissingError struct {
	Key string
}

func (e *CurrentRunPointerMissingError) Error() string {
	return fmt.Sprintf("%s: %q", ErrCurrentRunPointerMissing, e.Key)
}

func (e *CurrentRunPointerMissingError) Unwrap() error {
	return ErrCurrentRunPointerMissing
}

type CurrentManifestMissingError struct {
	Key string
}

func (e *CurrentManifestMissingError) Error() string {
	return fmt.Sprintf("%s: %q", ErrCurrentManifestMissing, e.Key)
}

func (e *CurrentManifestMissingError) Unwrap() error {
	return ErrCurrentManifestMissing
}

type CurrentState struct {
	SessionPrefix      string
	CurrentRunIDKey    string
	CurrentManifestKey string
	RunID              string
	Manifest           *manifest.Manifest
}

type CurrentStateValidation struct {
	ExpectedCampaign  string
	ExpectedSessionID string
	ExpectedRunID     string
	ValidateRunID     bool
}

func LoadCurrentRunPointer(ctx context.Context, store storage.ObjectStore, currentRunIDKey string) (string, error) {
	if store == nil {
		return "", fmt.Errorf("object store is required")
	}
	key := strings.TrimSpace(currentRunIDKey)
	if key == "" {
		return "", fmt.Errorf("current run pointer key is required")
	}

	exists, err := store.Exists(ctx, key)
	if err != nil {
		return "", fmt.Errorf("check current run pointer %q: %w", key, err)
	}
	if !exists {
		return "", &CurrentRunPointerMissingError{Key: key}
	}

	localPath, err := storage.DownloadObjectToTemp(ctx, store, key, "narratio-current-run-id-*.txt")
	if err != nil {
		return "", fmt.Errorf("download current run pointer %q: %w", key, err)
	}
	defer func() { _ = os.Remove(localPath) }()

	data, err := os.ReadFile(localPath)
	if err != nil {
		return "", fmt.Errorf("read downloaded current run pointer %q: %w", key, err)
	}
	runID := strings.TrimSpace(string(data))
	if runID == "" {
		return "", fmt.Errorf("current run pointer %q is empty", key)
	}
	return runID, nil
}

func LoadCurrentManifest(ctx context.Context, store storage.ObjectStore, currentManifestKey string) (*manifest.Manifest, error) {
	if store == nil {
		return nil, fmt.Errorf("object store is required")
	}
	key := strings.TrimSpace(currentManifestKey)
	if key == "" {
		return nil, fmt.Errorf("current manifest key is required")
	}

	exists, err := store.Exists(ctx, key)
	if err != nil {
		return nil, fmt.Errorf("check current manifest %q: %w", key, err)
	}
	if !exists {
		return nil, &CurrentManifestMissingError{Key: key}
	}

	localPath, err := storage.DownloadObjectToTemp(ctx, store, key, "narratio-current-manifest-*.json")
	if err != nil {
		return nil, fmt.Errorf("download current manifest %q: %w", key, err)
	}
	defer func() { _ = os.Remove(localPath) }()

	manifestStore := &manifest.LocalStore{}
	m, err := manifestStore.Load(ctx, localPath)
	if err != nil {
		return nil, fmt.Errorf("current manifest decode failed: %w", err)
	}
	return m, nil
}

func LoadCurrentState(
	ctx context.Context,
	store storage.ObjectStore,
	sessionPrefix string,
	validation CurrentStateValidation,
) (*CurrentState, error) {
	prefix := strings.TrimSpace(sessionPrefix)
	if prefix == "" {
		return nil, fmt.Errorf("session prefix is required")
	}
	currentManifestKey, currentRunIDKey := ResolveCurrentStateKeys(prefix)
	runID, err := LoadCurrentRunPointer(ctx, store, currentRunIDKey)
	if err != nil {
		return nil, err
	}
	m, err := LoadCurrentManifest(ctx, store, currentManifestKey)
	if err != nil {
		return nil, err
	}

	state := &CurrentState{
		SessionPrefix:      prefix,
		CurrentRunIDKey:    currentRunIDKey,
		CurrentManifestKey: currentManifestKey,
		RunID:              runID,
		Manifest:           m,
	}
	if err := ValidateCurrentStateIdentity(state, validation); err != nil {
		return nil, err
	}
	return state, nil
}

func ValidateCurrentStateIdentity(state *CurrentState, validation CurrentStateValidation) error {
	if state == nil || state.Manifest == nil {
		return fmt.Errorf("current state with manifest is required")
	}
	expectedSessionID := strings.TrimSpace(validation.ExpectedSessionID)
	expectedCampaign := strings.TrimSpace(validation.ExpectedCampaign)
	expectedRunID := strings.TrimSpace(validation.ExpectedRunID)
	manifestSessionID := strings.TrimSpace(state.Manifest.SessionID)
	manifestCampaign := strings.TrimSpace(state.Manifest.Campaign)
	manifestRunID := strings.TrimSpace(state.Manifest.RunID)

	if expectedSessionID != "" && manifestSessionID != expectedSessionID {
		return fmt.Errorf(
			"current manifest session_id %q does not match expected session_id %q",
			manifestSessionID,
			expectedSessionID,
		)
	}
	if expectedCampaign != "" {
		if manifestCampaign == "" {
			return fmt.Errorf("current manifest campaign is required")
		}
		if manifestCampaign != expectedCampaign {
			return fmt.Errorf(
				"current manifest campaign %q does not match expected campaign %q",
				manifestCampaign,
				expectedCampaign,
			)
		}
	}
	if expectedRunID == "" && validation.ValidateRunID {
		expectedRunID = strings.TrimSpace(state.RunID)
	}
	if expectedRunID != "" {
		if manifestRunID == "" {
			return fmt.Errorf("current manifest run_id is required")
		}
		if manifestRunID != expectedRunID {
			return fmt.Errorf(
				"current run pointer %q references run %q but current manifest run_id is %q",
				state.CurrentRunIDKey,
				expectedRunID,
				manifestRunID,
			)
		}
	}
	return nil
}