package publish

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	"gitea.maximumdirect.net/eric/distributor/internal/config"
	"gitea.maximumdirect.net/eric/distributor/internal/state"
	"gitea.maximumdirect.net/eric/distributor/internal/storage"
)

func Execute(ctx context.Context, req Request, plan Plan) error {
	plan.Reconciliation = normalizeReconciliation(plan.Reconciliation)
	switch plan.Action {
	case ActionSkipSame, ActionSkipDestinationNewer:
		return nil
	case ActionPublishNew, ActionReplaceOlder, ActionForceReplace:
	default:
		return fmt.Errorf("cannot execute action %s: %s", plan.Action, plan.Reason)
	}

	if plan.Action == ActionReplaceOlder {
		if plan.ExistingState == nil {
			return fmt.Errorf("replace requires existing destination state")
		}
		if plan.Reconciliation.Mode == config.ReconciliationModeReplace {
			if err := req.DestinationBackend.DeleteManagedBundle(ctx, req.DestinationBundlePath, state.ManagedOutputPaths(*plan.ExistingState), storage.DeleteOptions{IgnoreMissing: true, PruneEmptyDirs: true}); err != nil {
				return err
			}
			if err := ensureDestinationEmpty(ctx, req.DestinationBackend, req.DestinationBundlePath); err != nil {
				return err
			}
		}
	}
	if plan.Action == ActionForceReplace {
		if err := req.DestinationBackend.DeletePrefix(ctx, req.DestinationBundlePath, storage.DeleteOptions{IgnoreMissing: true, PruneEmptyDirs: true}); err != nil {
			return err
		}
		if err := ensureDestinationEmpty(ctx, req.DestinationBackend, req.DestinationBundlePath); err != nil {
			return err
		}
	}
	if usesMergeRetention(plan) {
		if err := ensureMergeOutputPaths(ctx, req.DestinationBackend, req.DestinationBundlePath, plan); err != nil {
			return err
		}
	}

	writtenOutputs := make([]Output, 0, len(plan.Outputs))
	newOutputs := make([]Output, 0, len(plan.Outputs))
	cleanup := func() {
		outputs := writtenOutputs
		if usesMergeRetention(plan) {
			outputs = newOutputs
		}
		_ = req.DestinationBackend.DeleteManagedBundle(ctx, req.DestinationBundlePath, ManagedOutputPaths(outputs), storage.DeleteOptions{IgnoreMissing: true, PruneEmptyDirs: true})
	}
	for _, output := range plan.Outputs {
		destinationPath, err := storage.Join(req.DestinationBundlePath, output.DestinationPath)
		if err != nil {
			cleanup()
			return err
		}
		data := output.Data
		if output.Kind == state.OutputKindSource {
			sourcePath, err := storage.Join(req.SourceBundle.RootRelativePath, output.SourcePath)
			if err != nil {
				cleanup()
				return err
			}
			data, err = req.SourceBackend.ReadFile(ctx, sourcePath)
			if err != nil {
				cleanup()
				return err
			}
		}
		managed := outputManagedByExistingState(output, plan.ExistingState)
		if _, err := req.DestinationBackend.WriteFile(ctx, destinationPath, data, storage.WriteOptions{Overwrite: managed && usesMergeRetention(plan), PreferAtomic: true}); err != nil {
			cleanup()
			return err
		}
		writtenOutputs = append(writtenOutputs, output)
		if !managed {
			newOutputs = append(newOutputs, output)
		}
	}

	now := time.Now().UTC()
	createdAt := now
	if plan.ExistingState != nil {
		createdAt = plan.ExistingState.CreatedAt
	}
	stateOutputs, err := stateOutputsForPlan(plan, now)
	if err != nil {
		cleanup()
		return err
	}
	destinationState := state.DistributorState{
		SchemaVersion:      state.SchemaVersion,
		DistributorVersion: req.DistributorVersion,
		PipelineID:         req.PipelineID,
		DestinationID:      req.DestinationID,
		PublishedAt:        now,
		CreatedAt:          createdAt,
		UpdatedAt:          now,
		State:              state.StatePolicy{Mode: state.StateModeSingleOwner},
		Reconciliation:     state.ReconciliationPolicy{Mode: plan.Reconciliation.Mode},
		Source:             state.SourceState{Manifest: req.SourceBundle.Manifest},
		Outputs:            stateOutputs,
	}
	if plan.PrimaryURL != "" {
		destinationState.Links = &state.LinkState{PrimaryURL: plan.PrimaryURL}
	}
	if err := state.Validate(destinationState); err != nil {
		cleanup()
		return err
	}
	data, err := json.MarshalIndent(destinationState, "", "  ")
	if err != nil {
		cleanup()
		return err
	}
	data = append(data, '\n')
	statePath, err := storage.StatePath(req.DestinationBundlePath)
	if err != nil {
		cleanup()
		return err
	}
	if _, err := req.DestinationBackend.WriteFile(ctx, statePath, data, storage.WriteOptions{Overwrite: plan.ExistingState != nil, PreferAtomic: true}); err != nil {
		cleanup()
		return err
	}
	return nil
}

func ensureMergeOutputPaths(ctx context.Context, backend storage.Backend, bundlePath string, plan Plan) error {
	for _, output := range plan.Outputs {
		if outputManagedByExistingState(output, plan.ExistingState) {
			continue
		}
		destinationPath, err := storage.Join(bundlePath, output.DestinationPath)
		if err != nil {
			return err
		}
		if _, err := backend.Stat(ctx, destinationPath); err == nil {
			return fmt.Errorf("merge output path %s exists but is not managed by destination state", storage.DisplayPath(output.DestinationPath))
		} else if !storage.IsNotFound(err) {
			return err
		}
	}
	return nil
}

func outputManagedByExistingState(output Output, existing *state.DistributorState) bool {
	if existing == nil {
		return false
	}
	_, ok := state.FindOutputByPath(existing.Outputs, output.DestinationPath)
	return ok
}

func stateOutputsForPlan(plan Plan, now time.Time) ([]state.OutputFile, error) {
	existingOutputs := []state.OutputFile(nil)
	if plan.ExistingState != nil {
		existingOutputs = plan.ExistingState.Outputs
	}
	planned := state.ProjectOutputs(StateOutputProjections(plan.Outputs), existingOutputs, now)
	if !usesMergeRetention(plan) || plan.ExistingState == nil {
		return planned, nil
	}
	return state.MergeOutputFiles(plan.ExistingState.Outputs, planned)
}

func usesMergeRetention(plan Plan) bool {
	return plan.Reconciliation.Mode == config.ReconciliationModeMerge && plan.Action == ActionReplaceOlder
}