package store

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

	"ai-service/internal/model"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

type Store struct {
	pool *pgxpool.Pool
}

const jobSelectColumns = `
id, owner_service, owner_ref, task_type, model_profile, priority, status,
attempts, max_attempts, input, result, error_code, error_message,
scheduled_at, started_at, completed_at, worker_id, heartbeat_at,
created_at, updated_at, idempotency_key
`

func Open(ctx context.Context, databaseURL string) (*Store, error) {
	if strings.TrimSpace(databaseURL) == "" {
		return nil, errors.New("DATABASE_URL is required")
	}
	cfg, err := pgxpool.ParseConfig(databaseURL)
	if err != nil {
		return nil, fmt.Errorf("parse database url: %w", err)
	}
	pool, err := pgxpool.NewWithConfig(ctx, cfg)
	if err != nil {
		return nil, fmt.Errorf("connect postgres: %w", err)
	}
	if err := pool.Ping(ctx); err != nil {
		pool.Close()
		return nil, fmt.Errorf("ping postgres: %w", err)
	}
	return &Store{pool: pool}, nil
}

func (s *Store) Close() {
	s.pool.Close()
}

func (s *Store) Ping(ctx context.Context) error {
	return s.pool.Ping(ctx)
}

func (s *Store) Exec(ctx context.Context, sql string, args ...any) error {
	_, err := s.pool.Exec(ctx, sql, args...)
	return err
}

func (s *Store) CreateJob(ctx context.Context, in model.CreateJob) (*model.Job, error) {
	if err := validateCreateJob(in); err != nil {
		return nil, err
	}
	if in.MaxAttempts <= 0 {
		in.MaxAttempts = 3
	}
	if len(in.Input) == 0 {
		in.Input = json.RawMessage(`{}`)
	}
	scheduledAt := time.Now().UTC()
	if in.ScheduledAt != nil {
		scheduledAt = in.ScheduledAt.UTC()
	}

	const q = `
INSERT INTO ai_jobs (
  owner_service, owner_ref, task_type, model_profile, priority, max_attempts,
  input, scheduled_at, idempotency_key
)
VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9)
ON CONFLICT (idempotency_key) WHERE idempotency_key IS NOT NULL
DO UPDATE SET updated_at = ai_jobs.updated_at
RETURNING ` + jobSelectColumns + `
`
	row := s.pool.QueryRow(ctx, q,
		in.OwnerService,
		in.OwnerRef,
		in.TaskType,
		in.ModelProfile,
		in.Priority,
		in.MaxAttempts,
		in.Input,
		scheduledAt,
		in.IdempotencyKey,
	)
	return scanJob(row)
}

func validateCreateJob(in model.CreateJob) error {
	switch {
	case strings.TrimSpace(in.OwnerService) == "":
		return errors.New("owner_service is required")
	case strings.TrimSpace(in.OwnerRef) == "":
		return errors.New("owner_ref is required")
	case strings.TrimSpace(in.TaskType) == "":
		return errors.New("task_type is required")
	case strings.TrimSpace(in.ModelProfile) == "":
		return errors.New("model_profile is required")
	default:
		return nil
	}
}

func (s *Store) GetJob(ctx context.Context, id uuid.UUID) (*model.Job, error) {
	const q = `
SELECT id, owner_service, owner_ref, task_type, model_profile, priority, status,
       attempts, max_attempts, input, result, error_code, error_message,
       scheduled_at, started_at, completed_at, worker_id, heartbeat_at,
       created_at, updated_at, idempotency_key
FROM ai_jobs
WHERE id = $1
`
	job, err := scanJob(s.pool.QueryRow(ctx, q, id))
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, nil
	}
	return job, err
}

func (s *Store) RetryJob(ctx context.Context, id uuid.UUID) (*model.Job, error) {
	const q = `
UPDATE ai_jobs
SET status = 'pending',
    attempts = 0,
    started_at = NULL,
    completed_at = NULL,
    error_code = NULL,
    error_message = NULL,
    worker_id = NULL,
    heartbeat_at = NULL,
    scheduled_at = NOW(),
    updated_at = NOW()
WHERE id = $1
  AND status IN ('failed', 'running')
RETURNING id, owner_service, owner_ref, task_type, model_profile, priority, status,
          attempts, max_attempts, input, result, error_code, error_message,
          scheduled_at, started_at, completed_at, worker_id, heartbeat_at,
          created_at, updated_at, idempotency_key
`
	job, err := scanJob(s.pool.QueryRow(ctx, q, id))
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, nil
	}
	return job, err
}

func (s *Store) ClaimJobs(ctx context.Context, in model.ClaimJobs) ([]*model.Job, error) {
	if in.Limit <= 0 {
		in.Limit = 1
	}
	if in.Limit > 100 {
		in.Limit = 100
	}
	workerID := strings.TrimSpace(in.WorkerID)
	if workerID == "" {
		workerID = "unknown"
	}
	if in.TaskTypes == nil {
		in.TaskTypes = []string{}
	}
	if in.ModelProfiles == nil {
		in.ModelProfiles = []string{}
	}
	const q = `
WITH picked AS (
  SELECT id
  FROM ai_jobs
  WHERE status = 'pending'
    AND attempts < max_attempts
    AND scheduled_at <= NOW()
    AND (cardinality($1::text[]) = 0 OR task_type = ANY($1::text[]))
    AND (cardinality($2::text[]) = 0 OR model_profile = ANY($2::text[]))
  ORDER BY priority DESC, scheduled_at ASC, created_at ASC
  LIMIT $3
  FOR UPDATE SKIP LOCKED
)
UPDATE ai_jobs j
SET status = 'running',
    attempts = j.attempts + 1,
    started_at = NOW(),
    completed_at = NULL,
    error_code = NULL,
    error_message = NULL,
    worker_id = $4,
    heartbeat_at = NOW(),
    updated_at = NOW()
FROM picked
WHERE j.id = picked.id
RETURNING ` + jobSelectColumns + `
`
	rows, err := s.pool.Query(ctx, q, in.TaskTypes, in.ModelProfiles, in.Limit, workerID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []*model.Job
	for rows.Next() {
		job, err := scanJob(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, job)
	}
	return out, rows.Err()
}

func (s *Store) CompleteJob(ctx context.Context, id uuid.UUID, in model.CompleteJob) (*model.Job, error) {
	if len(in.Result) == 0 {
		in.Result = json.RawMessage(`{}`)
	}
	const q = `
UPDATE ai_jobs
SET status = 'done',
    result = $2,
    error_code = NULL,
    error_message = NULL,
    completed_at = NOW(),
    heartbeat_at = NOW(),
    updated_at = NOW()
WHERE id = $1
  AND status = 'running'
RETURNING ` + jobSelectColumns + `
`
	job, err := scanJob(s.pool.QueryRow(ctx, q, id, in.Result))
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, nil
	}
	return job, err
}

func (s *Store) FailJob(ctx context.Context, id uuid.UUID, in model.FailJob) (*model.Job, error) {
	errorCode := strings.TrimSpace(in.ErrorCode)
	if errorCode == "" {
		errorCode = "unknown"
	}
	errorMessage := strings.TrimSpace(in.ErrorMessage)
	const q = `
UPDATE ai_jobs
SET status = 'failed',
    error_code = $2,
    error_message = $3,
    completed_at = NOW(),
    heartbeat_at = NOW(),
    updated_at = NOW()
WHERE id = $1
  AND status = 'running'
RETURNING ` + jobSelectColumns + `
`
	job, err := scanJob(s.pool.QueryRow(ctx, q, id, errorCode, errorMessage))
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, nil
	}
	return job, err
}

func (s *Store) Stats(ctx context.Context) (*model.Stats, error) {
	out := &model.Stats{At: time.Now().UTC()}

	queueRows, err := s.pool.Query(ctx, `
SELECT task_type, model_profile, status, count(*)
FROM ai_jobs
GROUP BY task_type, model_profile, status
ORDER BY task_type, model_profile, status
`)
	if err != nil {
		return nil, err
	}
	defer queueRows.Close()
	for queueRows.Next() {
		var stat model.QueueStat
		if err := queueRows.Scan(&stat.TaskType, &stat.ModelProfile, &stat.Status, &stat.Total); err != nil {
			return nil, err
		}
		out.Queues = append(out.Queues, stat)
	}
	if err := queueRows.Err(); err != nil {
		return nil, err
	}

	errorRows, err := s.pool.Query(ctx, `
SELECT task_type, model_profile, COALESCE(NULLIF(error_code, ''), 'unknown') AS error_code,
       count(*) AS total,
       count(*) FILTER (WHERE updated_at > NOW() - INTERVAL '24 hours') AS last_24h
FROM ai_jobs
WHERE status = 'failed'
GROUP BY task_type, model_profile, COALESCE(NULLIF(error_code, ''), 'unknown')
ORDER BY last_24h DESC, total DESC
`)
	if err != nil {
		return nil, err
	}
	defer errorRows.Close()
	for errorRows.Next() {
		var stat model.ErrorStat
		if err := errorRows.Scan(&stat.TaskType, &stat.ModelProfile, &stat.ErrorCode, &stat.Total, &stat.Last24h); err != nil {
			return nil, err
		}
		out.Errors = append(out.Errors, stat)
	}
	return out, errorRows.Err()
}

func scanJob(row pgx.Row) (*model.Job, error) {
	var job model.Job
	var input []byte
	var result []byte
	err := row.Scan(
		&job.ID,
		&job.OwnerService,
		&job.OwnerRef,
		&job.TaskType,
		&job.ModelProfile,
		&job.Priority,
		&job.Status,
		&job.Attempts,
		&job.MaxAttempts,
		&input,
		&result,
		&job.ErrorCode,
		&job.ErrorMessage,
		&job.ScheduledAt,
		&job.StartedAt,
		&job.CompletedAt,
		&job.WorkerID,
		&job.HeartbeatAt,
		&job.CreatedAt,
		&job.UpdatedAt,
		&job.IdempotencyKey,
	)
	if err != nil {
		return nil, err
	}
	job.Input = json.RawMessage(input)
	if len(result) > 0 {
		job.Result = json.RawMessage(result)
	}
	return &job, nil
}