package app

import (
	"context"
	"fmt"
	"io"
	"path"
	"path/filepath"
	"strings"

	"gitea.maximumdirect.net/eric/narratio/internal/config"
	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
)

func prepareRestoredManifest(
	ctx context.Context,
	cfg *config.Config,
	current *RemoteCurrentState,
	source io.Reader,
	destinationRoot string,
	requireCurrentIdentity bool,
) (*manifest.Manifest, error) {
	manifestStore := &manifest.LocalStore{}
	m, err := manifestStore.LoadReader(ctx, source)
	if err != nil {
		return nil, fmt.Errorf("validate manifest decode: %w", err)
	}
	if requireCurrentIdentity {
		if err := validateRestoredManifestIdentity(cfg, current, m); err != nil {
			return nil, err
		}
	}
	if err := rebaseRestoredManifestPaths(cfg, m, destinationRoot); err != nil {
		return nil, err
	}
	return m, nil
}

func validateRestoredManifestIdentity(cfg *config.Config, current *RemoteCurrentState, m *manifest.Manifest) error {
	if cfg == nil || cfg.Session == nil {
		return fmt.Errorf("resolved session config is required")
	}
	requestedSession := strings.TrimSpace(cfg.Session.SessionID)
	requestedCampaign := strings.TrimSpace(cfg.Session.Campaign)
	manifestSession := strings.TrimSpace(m.SessionID)
	manifestCampaign := strings.TrimSpace(m.Campaign)
	if manifestSession != requestedSession {
		return fmt.Errorf("manifest session_id %q does not match requested session_id %q", manifestSession, requestedSession)
	}
	if manifestCampaign == "" {
		return fmt.Errorf("manifest campaign is required")
	}
	if manifestCampaign != requestedCampaign {
		return fmt.Errorf("manifest campaign %q does not match requested campaign %q", manifestCampaign, requestedCampaign)
	}
	if current != nil {
		if expected := strings.TrimSpace(current.SessionID); expected != "" && manifestSession != expected {
			return fmt.Errorf("manifest session_id %q does not match discovered session_id %q", manifestSession, expected)
		}
		if expected := strings.TrimSpace(current.Campaign); expected != "" && manifestCampaign != expected {
			return fmt.Errorf("manifest campaign %q does not match discovered campaign %q", manifestCampaign, expected)
		}
		if expected := strings.TrimSpace(current.RunID); expected != "" && strings.TrimSpace(m.RunID) != expected {
			return fmt.Errorf("manifest run_id %q does not match discovered run_id %q", strings.TrimSpace(m.RunID), expected)
		}
	}
	return nil
}

func rebaseRestoredManifestPaths(cfg *config.Config, m *manifest.Manifest, destinationRoot string) error {
	if cfg == nil || cfg.Pipeline == nil || m == nil {
		return fmt.Errorf("resolved config and manifest are required")
	}
	destinationRoot = filepath.Clean(strings.TrimSpace(destinationRoot))
	if destinationRoot == "" || destinationRoot == "." {
		return fmt.Errorf("restored manifest destination root is required")
	}
	producerRoot, hasProducerRoot := restoredManifestSessionRoot(m)
	rebase := func(field, value string) (string, error) {
		return rebaseRestoredLocalReference(field, value, producerRoot, hasProducerRoot, destinationRoot)
	}

	for i := range m.Inputs {
		value, err := rebase("inputs.path", m.Inputs[i].Path)
		if err != nil {
			return err
		}
		m.Inputs[i].Path = value
		// Spool and cache locations are host-local implementation details. They
		// are deliberately not authoritative after a restore.
		m.Inputs[i].SpoolPath = ""
		m.Inputs[i].CachePath = ""
	}
	for i := range m.Artifacts {
		value, err := rebase("artifacts.local_path", m.Artifacts[i].LocalPath)
		if err != nil {
			return err
		}
		m.Artifacts[i].LocalPath = value
	}
	for stageName, record := range m.Stages {
		if record == nil {
			continue
		}
		for i := range record.Outputs {
			value, err := rebase("stages."+stageName+".outputs.local_path", record.Outputs[i].LocalPath)
			if err != nil {
				return err
			}
			record.Outputs[i].LocalPath = value
		}
		// Logs and generated configuration files are invocation-local diagnostics,
		// not restored artifacts. Dropping them prevents a producer-machine path
		// from becoming a usable local reference.
		record.Logs = nil
		record.GeneratedConfigs = nil
	}

	if runID := strings.TrimSpace(m.RunID); runID != "" {
		m.LocalWorkDir = filepath.Join(destinationRoot, config.PathRunsDirSegment, runID)
	} else {
		m.LocalWorkDir = destinationRoot
	}
	m.LocalSpoolDir = ""
	// A post-publish cleanup record is authority to delete producer-local
	// directories. It must never cross a restore boundary.
	m.PostPublishCleanup = nil
	return nil
}

func restoredManifestSessionRoot(m *manifest.Manifest) (string, bool) {
	if m == nil {
		return "", false
	}
	runRoot := portableCleanPath(m.LocalWorkDir)
	runID := strings.TrimSpace(m.RunID)
	if !portableAbsolutePath(runRoot) || runID == "" || path.Base(runRoot) != runID {
		return "", false
	}
	runsDir := path.Dir(runRoot)
	if path.Base(runsDir) != config.PathRunsDirSegment {
		return "", false
	}
	return path.Dir(runsDir), true
}

func rebaseRestoredLocalReference(field, value, producerRoot string, hasProducerRoot bool, destinationRoot string) (string, error) {
	value = strings.TrimSpace(value)
	if value == "" {
		return "", nil
	}
	if portableDrivePath(value) && !portableAbsolutePath(value) {
		return "", fmt.Errorf("%s has an unsafe relative path %q", field, value)
	}
	if portableAbsolutePath(value) {
		if !hasProducerRoot {
			return "", fmt.Errorf("%s has an absolute path without a producer session root", field)
		}
		relative, ok := portableRelativeWithinRoot(producerRoot, value)
		if !ok || relative == "" {
			return "", fmt.Errorf("%s absolute path is outside the producer session root", field)
		}
		resolved, err := joinWithinSessionRoot(destinationRoot, relative)
		if err != nil {
			return "", fmt.Errorf("%s: %w", field, err)
		}
		return resolved, nil
	}
	resolved, err := joinWithinSessionRoot(destinationRoot, strings.ReplaceAll(value, "\\", "/"))
	if err != nil {
		return "", fmt.Errorf("%s has an unsafe relative path: %w", field, err)
	}
	return resolved, nil
}

func portableRelativeWithinRoot(root, candidate string) (string, bool) {
	root = strings.TrimSuffix(portableCleanPath(root), "/")
	candidate = portableCleanPath(candidate)
	if root == "" || candidate == "" {
		return "", false
	}
	compareRoot, compareCandidate := root, candidate
	if portableDrivePath(root) || portableDrivePath(candidate) || strings.HasPrefix(root, "//") || strings.HasPrefix(candidate, "//") {
		compareRoot = strings.ToLower(compareRoot)
		compareCandidate = strings.ToLower(compareCandidate)
	}
	if compareCandidate == compareRoot {
		return "", true
	}
	if !strings.HasPrefix(compareCandidate, compareRoot+"/") {
		return "", false
	}
	return strings.TrimPrefix(candidate, root+"/"), true
}

func portableCleanPath(value string) string {
	value = strings.ReplaceAll(strings.TrimSpace(value), "\\", "/")
	if value == "" {
		return ""
	}
	return path.Clean(value)
}

func portableAbsolutePath(value string) bool {
	value = strings.TrimSpace(value)
	return strings.HasPrefix(value, "/") || strings.HasPrefix(value, "\\") || (len(value) >= 3 && isASCIIAlpha(value[0]) && value[1] == ':' && (value[2] == '/' || value[2] == '\\'))
}

func portableDrivePath(value string) bool {
	value = strings.TrimSpace(value)
	return len(value) >= 2 && isASCIIAlpha(value[0]) && value[1] == ':'
}

func isASCIIAlpha(value byte) bool {
	return (value >= 'a' && value <= 'z') || (value >= 'A' && value <= 'Z')
}