package runtime

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"sync"

	"browser.local/run/protocol"
)

const jobJournalVersion = 1

type JobJournal struct {
	mu                 sync.Mutex
	path               string
	active             map[string]protocol.RunJobAssignment
	pendingResults     map[string]protocol.RunJobResultRequest
	pendingActivations map[string]string
}

type jobJournalFile struct {
	Version            int                            `json:"version"`
	Active             []protocol.RunJobAssignment    `json:"active"`
	PendingResults     []protocol.RunJobResultRequest `json:"pendingResults,omitempty"`
	PendingActivations map[string]string              `json:"pendingActivations,omitempty"`
}

func NewJobJournal() *JobJournal {
	return &JobJournal{active: map[string]protocol.RunJobAssignment{}, pendingResults: map[string]protocol.RunJobResultRequest{}, pendingActivations: map[string]string{}}
}

func NewPersistentJobJournal(workspaceRoot string) (*JobJournal, error) {
	if workspaceRoot == "" {
		workspaceRoot = filepath.Join(".", ".run-workspace")
	}
	dir := filepath.Join(workspaceRoot, "state")
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return nil, fmt.Errorf("create job journal directory: %w", err)
	}
	if err := os.Chmod(dir, 0o700); err != nil {
		return nil, fmt.Errorf("secure job journal directory: %w", err)
	}
	journal := &JobJournal{path: filepath.Join(dir, "jobs.json"), active: map[string]protocol.RunJobAssignment{}, pendingResults: map[string]protocol.RunJobResultRequest{}, pendingActivations: map[string]string{}}
	if err := journal.load(); err != nil {
		return nil, err
	}
	return journal, nil
}

func (journal *JobJournal) Store(job protocol.RunJobAssignment) error {
	journal.mu.Lock()
	defer journal.mu.Unlock()
	if err := validateJournalAssignment(job); err != nil {
		return err
	}
	previous, existed := journal.active[job.JobID]
	journal.active[job.JobID] = job
	if err := journal.persistLocked(); err != nil {
		if existed {
			journal.active[job.JobID] = previous
		} else {
			delete(journal.active, job.JobID)
		}
		return err
	}
	return nil
}

func (journal *JobJournal) Delete(jobID string) error {
	journal.mu.Lock()
	defer journal.mu.Unlock()
	previous, existed := journal.active[jobID]
	previousResult, hadResult := journal.pendingResults[jobID]
	previousActivation, hadActivation := journal.pendingActivations[jobID]
	delete(journal.active, jobID)
	delete(journal.pendingResults, jobID)
	delete(journal.pendingActivations, jobID)
	if err := journal.persistLocked(); err != nil {
		if existed {
			journal.active[jobID] = previous
		}
		if hadResult {
			journal.pendingResults[jobID] = previousResult
		}
		if hadActivation {
			journal.pendingActivations[jobID] = previousActivation
		}
		return err
	}
	return nil
}

func (journal *JobJournal) StorePendingResult(result protocol.RunJobResultRequest, activationManifest string) error {
	journal.mu.Lock()
	defer journal.mu.Unlock()
	assignment, exists := journal.active[result.JobID]
	if !exists || assignment.Attempt != result.Attempt || assignment.LeaseToken != result.LeaseToken || assignment.RunEndpointID != result.RunEndpointID {
		return fmt.Errorf("pending result does not match active journal attempt")
	}
	if result.State != "succeeded" && result.State != "failed" && result.State != "cancelled" {
		return fmt.Errorf("pending result state is not terminal")
	}
	result.SessionToken = ""
	previous, hadPrevious := journal.pendingResults[result.JobID]
	previousActivation, hadActivation := journal.pendingActivations[result.JobID]
	journal.pendingResults[result.JobID] = result
	if activationManifest != "" {
		journal.pendingActivations[result.JobID] = activationManifest
	} else {
		delete(journal.pendingActivations, result.JobID)
	}
	if err := journal.persistLocked(); err != nil {
		if hadPrevious {
			journal.pendingResults[result.JobID] = previous
		} else {
			delete(journal.pendingResults, result.JobID)
		}
		if hadActivation {
			journal.pendingActivations[result.JobID] = previousActivation
		} else {
			delete(journal.pendingActivations, result.JobID)
		}
		return err
	}
	return nil
}

func (journal *JobJournal) PendingActivation(jobID string) string {
	journal.mu.Lock()
	defer journal.mu.Unlock()
	return journal.pendingActivations[jobID]
}

func (journal *JobJournal) PendingResult(jobID string) (protocol.RunJobResultRequest, bool) {
	journal.mu.Lock()
	defer journal.mu.Unlock()
	result, exists := journal.pendingResults[jobID]
	return result, exists
}

func (journal *JobJournal) MarkActive(job protocol.RunJobAssignment) {
	_ = journal.Store(job)
}

func (journal *JobJournal) MarkTerminal(jobID string) {
	_ = journal.Delete(jobID)
}

func (journal *JobJournal) ActiveJobs() []protocol.RunJobAssignment {
	journal.mu.Lock()
	defer journal.mu.Unlock()
	jobs := make([]protocol.RunJobAssignment, 0, len(journal.active))
	for _, job := range journal.active {
		jobs = append(jobs, job)
	}
	sort.Slice(jobs, func(i, j int) bool { return jobs[i].JobID < jobs[j].JobID })
	return jobs
}

func (journal *JobJournal) ReconcileEntries() []protocol.RunJobReconcileEntry {
	jobs := journal.ActiveJobs()
	entries := make([]protocol.RunJobReconcileEntry, len(jobs))
	for i, job := range jobs {
		entries[i] = protocol.RunJobReconcileEntry{JobID: job.JobID, LeaseToken: job.LeaseToken, Attempt: job.Attempt}
	}
	return entries
}

func (journal *JobJournal) ActiveJobIDs() []string {
	jobs := journal.ActiveJobs()
	ids := make([]string, len(jobs))
	for i, job := range jobs {
		ids[i] = job.JobID
	}
	return ids
}

func (journal *JobJournal) ActiveCount() int {
	journal.mu.Lock()
	defer journal.mu.Unlock()
	return len(journal.active)
}

func (journal *JobJournal) load() error {
	payload, err := os.ReadFile(journal.path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil
		}
		return fmt.Errorf("read job journal: %w", err)
	}
	var snapshot jobJournalFile
	if err := json.Unmarshal(payload, &snapshot); err != nil {
		return fmt.Errorf("decode job journal: %w", err)
	}
	if snapshot.Version != jobJournalVersion {
		return fmt.Errorf("unsupported job journal version %d", snapshot.Version)
	}
	for _, job := range snapshot.Active {
		if err := validateJournalAssignment(job); err != nil {
			return fmt.Errorf("invalid job journal entry: %w", err)
		}
		if _, exists := journal.active[job.JobID]; exists {
			return fmt.Errorf("duplicate job journal entry %q", job.JobID)
		}
		journal.active[job.JobID] = job
	}
	for _, result := range snapshot.PendingResults {
		assignment, exists := journal.active[result.JobID]
		if !exists || result.SessionToken != "" || assignment.Attempt != result.Attempt || assignment.LeaseToken != result.LeaseToken || assignment.RunEndpointID != result.RunEndpointID {
			return fmt.Errorf("invalid pending result journal entry for %q", result.JobID)
		}
		if _, duplicate := journal.pendingResults[result.JobID]; duplicate {
			return fmt.Errorf("duplicate pending result journal entry %q", result.JobID)
		}
		journal.pendingResults[result.JobID] = result
	}
	for jobID, manifest := range snapshot.PendingActivations {
		if _, exists := journal.pendingResults[jobID]; !exists || manifest == "" {
			return fmt.Errorf("invalid pending activation journal entry for %q", jobID)
		}
		journal.pendingActivations[jobID] = manifest
	}
	return nil
}

func (journal *JobJournal) persistLocked() error {
	if journal.path == "" {
		return nil
	}
	jobs := make([]protocol.RunJobAssignment, 0, len(journal.active))
	for _, job := range journal.active {
		jobs = append(jobs, job)
	}
	sort.Slice(jobs, func(i, j int) bool { return jobs[i].JobID < jobs[j].JobID })
	results := make([]protocol.RunJobResultRequest, 0, len(journal.pendingResults))
	for _, result := range journal.pendingResults {
		result.SessionToken = ""
		results = append(results, result)
	}
	sort.Slice(results, func(i, j int) bool { return results[i].JobID < results[j].JobID })
	activations := make(map[string]string, len(journal.pendingActivations))
	for jobID, manifest := range journal.pendingActivations {
		activations[jobID] = manifest
	}
	payload, err := json.MarshalIndent(jobJournalFile{Version: jobJournalVersion, Active: jobs, PendingResults: results, PendingActivations: activations}, "", "  ")
	if err != nil {
		return fmt.Errorf("encode job journal: %w", err)
	}
	temporary := journal.path + ".tmp"
	file, err := os.OpenFile(temporary, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0o600)
	if err != nil {
		return fmt.Errorf("open temporary job journal: %w", err)
	}
	removeTemporary := true
	defer func() {
		_ = file.Close()
		if removeTemporary {
			_ = os.Remove(temporary)
		}
	}()
	if _, err := file.Write(payload); err != nil {
		return fmt.Errorf("write job journal: %w", err)
	}
	if err := file.Sync(); err != nil {
		return fmt.Errorf("sync job journal: %w", err)
	}
	if err := file.Close(); err != nil {
		return fmt.Errorf("close job journal: %w", err)
	}
	if err := os.Rename(temporary, journal.path); err != nil {
		return fmt.Errorf("replace job journal: %w", err)
	}
	removeTemporary = false
	if err := os.Chmod(journal.path, 0o600); err != nil {
		return fmt.Errorf("secure job journal: %w", err)
	}
	return nil
}

func validateJournalAssignment(job protocol.RunJobAssignment) error {
	if err := protocol.ValidateRunJobAssignment(job); err != nil {
		return err
	}
	if job.Attempt <= 0 || job.LeaseToken == "" {
		return fmt.Errorf("job attempt and lease token are required")
	}
	return nil
}