package usecase

import (
	"context"
	"fmt"
	"time"

	"github.com/google/uuid"

	"github.com/emil28092005/SciMesh/coordinator/internal/domain"
)

// UIReadRepository is a read-only projection source for the local operator UI.
// It intentionally exposes no storage paths or credentials.
type UIReadRepository interface {
	GetJob(ctx context.Context, jobID uuid.UUID) (*domain.Job, error)
	ListJobs(ctx context.Context, limit int) ([]domain.Job, error)
	ListTasksByJob(ctx context.Context, jobID uuid.UUID) ([]domain.Task, error)
	ListTasksByJobs(ctx context.Context, jobIDs []uuid.UUID) (map[uuid.UUID][]domain.Task, error)
	ListWorkers(ctx context.Context, limit int) ([]domain.Worker, error)
	ListArtifactsByJob(ctx context.Context, jobID uuid.UUID) ([]domain.Artifact, error)
}

type JobCard struct {
	ID               string     `json:"id"`
	Workload         string     `json:"workload"`
	Status           string     `json:"status"`
	CreatedAt        time.Time  `json:"created_at"`
	CompletedAt      *time.Time `json:"completed_at,omitempty"`
	ReducerStartedAt *time.Time `json:"reducer_started_at,omitempty"`
	ErrorCode        string     `json:"error_code,omitempty"`
	ErrorMessage     string     `json:"error_message,omitempty"`
	Total            int        `json:"total"`
	Pending          int        `json:"pending"`
	Leased           int        `json:"leased"`
	Running          int        `json:"running"`
	Completed        int        `json:"completed"`
	Failed           int        `json:"failed"`
	Cancelled        int        `json:"cancelled"`
}

type TaskCard struct {
	ID             string     `json:"id"`
	ChunkIndex     int        `json:"chunk_index"`
	Status         string     `json:"status"`
	Attempt        int        `json:"attempt"`
	MaxAttempts    int        `json:"max_attempts"`
	LeaseOwner     string     `json:"lease_owner,omitempty"`
	LeaseExpiresAt *time.Time `json:"lease_expires_at,omitempty"`
	StartedAt      *time.Time `json:"started_at,omitempty"`
	CompletedAt    *time.Time `json:"completed_at,omitempty"`
	ErrorCode      string     `json:"error_code,omitempty"`
	ErrorMessage   string     `json:"error_message,omitempty"`
}

// ParameterCard is an intentionally small allowlist of run configuration that
// helps an operator verify what is being computed without exposing arbitrary
// job payloads to the browser.
type ParameterCard struct {
	Label string `json:"label"`
	Value string `json:"value"`
}

type ArtifactCard struct {
	ID           string `json:"id"`
	Kind         string `json:"kind"`
	Filename     string `json:"filename"`
	SizeBytes    int64  `json:"size_bytes"`
	SHA256       string `json:"sha256"`
	Downloadable bool   `json:"downloadable"`
	Diagnostic   bool   `json:"diagnostic"`
}

type WorkerCard struct {
	ID              string    `json:"id"`
	Name            string    `json:"name"`
	Status          string    `json:"status"`
	Capabilities    []string  `json:"capabilities"`
	LastHeartbeatAt time.Time `json:"last_heartbeat_at"`
}

type DashboardView struct {
	Jobs          []JobCard    `json:"jobs"`
	Workers       []WorkerCard `json:"workers"`
	ActiveJobs    int          `json:"active_jobs"`
	FinishedJobs  int          `json:"finished_jobs"`
	OnlineWorkers int          `json:"online_workers"`
}
type JobDetailView struct {
	JobCard
	Tasks                []TaskCard      `json:"tasks"`
	Artifacts            []ArtifactCard  `json:"artifacts"`
	Parameters           []ParameterCard `json:"parameters"`
	FinalResultAvailable bool            `json:"final_result_available"`
}

type Dashboard struct{ read UIReadRepository }

func NewDashboard(read UIReadRepository) *Dashboard { return &Dashboard{read: read} }

func (d *Dashboard) Overview(ctx context.Context, limit int) (DashboardView, error) {
	jobs, err := d.read.ListJobs(ctx, limit)
	if err != nil {
		return DashboardView{}, err
	}
	workers, err := d.read.ListWorkers(ctx, limit)
	if err != nil {
		return DashboardView{}, err
	}
	out := DashboardView{Jobs: make([]JobCard, 0, len(jobs)), Workers: make([]WorkerCard, 0, len(workers))}
	jobIDs := make([]uuid.UUID, 0, len(jobs))
	for _, job := range jobs {
		jobIDs = append(jobIDs, job.ID)
	}
	tasksByJob, err := d.read.ListTasksByJobs(ctx, jobIDs)
	if err != nil {
		return DashboardView{}, err
	}
	for _, job := range jobs {
		card := jobCard(job, tasksByJob[job.ID])
		out.Jobs = append(out.Jobs, card)
		switch card.Status {
		case string(domain.JobCompleted), string(domain.JobFailed), string(domain.JobCancelled):
			out.FinishedJobs++
		default:
			out.ActiveJobs++
		}
	}
	for _, worker := range workers {
		out.Workers = append(out.Workers, WorkerCard{ID: worker.ID.String(), Name: worker.Name, Status: string(worker.Status), Capabilities: worker.Capabilities, LastHeartbeatAt: worker.LastHeartbeatAt})
		if worker.Status == domain.WorkerOnline || worker.Status == domain.WorkerBusy {
			out.OnlineWorkers++
		}
	}
	return out, nil
}

func (d *Dashboard) JobDetail(ctx context.Context, jobID uuid.UUID) (JobDetailView, error) {
	job, err := d.read.GetJob(ctx, jobID)
	if err != nil {
		return JobDetailView{}, err
	}
	tasks, err := d.read.ListTasksByJob(ctx, jobID)
	if err != nil {
		return JobDetailView{}, err
	}
	artifacts, err := d.read.ListArtifactsByJob(ctx, jobID)
	if err != nil {
		return JobDetailView{}, err
	}
	workers, err := d.read.ListWorkers(ctx, 100)
	if err != nil {
		return JobDetailView{}, err
	}
	workerNames := make(map[string]string, len(workers))
	for _, worker := range workers {
		workerNames[worker.ID.String()] = worker.Name
	}
	out := JobDetailView{
		JobCard:    jobCard(*job, tasks),
		Tasks:      make([]TaskCard, 0, len(tasks)),
		Artifacts:  make([]ArtifactCard, 0, len(artifacts)),
		Parameters: uiParameters(job.Parameters),
	}
	for _, task := range tasks {
		card := TaskCard{ID: task.ID.String(), ChunkIndex: task.ChunkIndex, Status: string(task.Status), Attempt: task.Attempt, MaxAttempts: task.MaxAttempts, LeaseExpiresAt: task.LeaseExpiresAt, StartedAt: task.StartedAt, CompletedAt: task.CompletedAt}
		if task.LeaseOwner != nil {
			card.LeaseOwner = workerNames[*task.LeaseOwner]
			if card.LeaseOwner == "" {
				card.LeaseOwner = "Worker " + shortID(*task.LeaseOwner)
			}
		}
		if task.ErrorCode != nil {
			card.ErrorCode = *task.ErrorCode
		}
		if task.ErrorMessage != nil {
			card.ErrorMessage = *task.ErrorMessage
		}
		out.Tasks = append(out.Tasks, card)
	}
	for _, artifact := range artifacts {
		diagnostic := artifact.Kind == domain.ArtifactPartialResult
		downloadable := previewableArtifact(*job, artifact)
		out.Artifacts = append(out.Artifacts, ArtifactCard{ID: artifact.ID.String(), Kind: string(artifact.Kind), Filename: artifact.Filename, SizeBytes: artifact.SizeBytes, SHA256: artifact.SHA256, Downloadable: downloadable, Diagnostic: diagnostic})
		if artifact.Kind == domain.ArtifactFinalResult && downloadable {
			out.FinalResultAvailable = true
		}
	}
	return out, nil
}

// DownloadableArtifactBelongsToJob applies the same policy used by the UI
// projection: partial diagnostics and the persisted final result are public to
// the operator; source inputs and shards are not exposed through a guessed UI
// URL.
func (d *Dashboard) DownloadableArtifactBelongsToJob(ctx context.Context, jobID, artifactID uuid.UUID) (bool, error) {
	job, err := d.read.GetJob(ctx, jobID)
	if err != nil {
		return false, err
	}
	artifacts, err := d.read.ListArtifactsByJob(ctx, jobID)
	if err != nil {
		return false, err
	}
	for _, a := range artifacts {
		if a.ID == artifactID && previewableArtifact(*job, a) {
			return true, nil
		}
	}
	return false, nil
}

func jobCard(job domain.Job, tasks []domain.Task) JobCard {
	c := JobCard{ID: job.ID.String(), Workload: job.Workload, CreatedAt: job.CreatedAt, CompletedAt: job.CompletedAt, ReducerStartedAt: job.ReducerStartedAt}
	if job.ErrorCode != nil {
		c.ErrorCode = *job.ErrorCode
	}
	if job.ErrorMessage != nil {
		c.ErrorMessage = *job.ErrorMessage
	}
	for _, task := range tasks {
		c.Total++
		switch task.Status {
		case domain.TaskPending:
			c.Pending++
		case domain.TaskLeased:
			c.Leased++
		case domain.TaskRunning:
			c.Running++
		case domain.TaskCompleted:
			c.Completed++
		case domain.TaskFailed:
			c.Failed++
		case domain.TaskCancelled:
			c.Cancelled++
		}
	}
	p := domain.JobProgress{Job: job, Total: c.Total, Pending: c.Pending, Leased: c.Leased + c.Running, Done: c.Completed, Failed: c.Failed, Cancelled: c.Cancelled}
	c.Status = string(p.DeriveStatus())
	return c
}

func uiParameters(parameters map[string]any) []ParameterCard {
	keys := []struct {
		key   string
		label string
	}{
		{"query_smiles", "Target SMILES"},
		{"query_id", "Target ChEMBL ID"},
		{"top_k", "Global top-k"},
		{"threshold", "Similarity threshold"},
		{"threshold_direction", "Threshold direction"},
	}
	out := make([]ParameterCard, 0, len(keys))
	for _, entry := range keys {
		value, ok := parameters[entry.key]
		if !ok {
			continue
		}
		formatted, ok := formatUIParameter(value)
		if ok {
			out = append(out, ParameterCard{Label: entry.label, Value: formatted})
		}
	}
	return out
}

func formatUIParameter(value any) (string, bool) {
	switch typed := value.(type) {
	case string:
		return typed, true
	case int, int64, float64, bool:
		return fmt.Sprint(typed), true
	default:
		return "", false
	}
}

func shortID(value string) string {
	if len(value) <= 8 {
		return value
	}
	return value[:8]
}