package ci

import (
	"bufio"
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"xorm.io/xorm"

	"github.com/forgeo/forgebucket/internal/events"
	"github.com/forgeo/forgebucket/internal/models"
)

// JobContext holds everything needed to execute a single pipeline job.
type JobContext struct {
	Run   models.PipelineRun
	Job   models.PipelineJob
	Steps []models.PipelineStep
	Repo  models.Repository
}

// ExecuteJob runs all steps of a job inside isolated Docker containers,
// streams log output to NATS and the DB, then publishes job.completed or job.failed.
func ExecuteJob(ctx context.Context, db *xorm.Engine, bus events.EventBus, jc JobContext, workspaceRoot string) {
	now := time.Now().UTC()
	jc.Job.Status = "running"
	jc.Job.StartedAt = &now
	db.ID(jc.Job.ID).Cols("status", "started_at").Update(&jc.Job) //nolint:errcheck

	// Extract repo snapshot into a workspace directory.
	workDir, err := extractWorkspace(jc.Repo.DiskPath, jc.Run.TriggerSHA, workspaceRoot, jc.Run.ID)
	if err != nil {
		failJob(db, bus, jc, fmt.Sprintf("workspace setup failed: %v", err))
		return
	}
	defer os.RemoveAll(workDir)

	image := jc.Job.Image
	if image == "" {
		image = "ubuntu:22.04"
	}

	// Pull image once per job (non-fatal if pull fails and image exists locally).
	pullCmd := exec.CommandContext(ctx, "docker", "pull", image)
	pullCmd.Run() //nolint:errcheck

	for i := range jc.Steps {
		step := &jc.Steps[i]
		if step.UsesAction == "checkout" {
			// Built-in checkout: workspace is already set up by extractWorkspace.
			markStep(db, step, "succeeded", 0)
			continue
		}
		if step.RunCmd == "" {
			markStep(db, step, "skipped", 0)
			continue
		}
		exitCode, err := runStep(ctx, db, bus, jc.Run.ID, jc.Job.ID, step, image, workDir)
		if err != nil || exitCode != 0 {
			if exitCode == 0 {
				exitCode = 1
			}
			markStep(db, step, "failed", exitCode)
			failJob(db, bus, jc, fmt.Sprintf("step %q exited %d", step.Name, exitCode))
			return
		}
		markStep(db, step, "succeeded", 0)
	}

	fin := time.Now().UTC()
	jc.Job.Status = "succeeded"
	jc.Job.FinishedAt = &fin
	db.ID(jc.Job.ID).Cols("status", "finished_at").Update(&jc.Job) //nolint:errcheck
	bus.Publish(events.SubjectJobCompleted, events.JobEvent{ //nolint:errcheck
		RunID: jc.Run.ID, JobID: jc.Job.ID, Status: "succeeded", At: fin,
	})
}

// runStep runs a single shell-command step inside a Docker container.
func runStep(ctx context.Context, db *xorm.Engine, bus events.EventBus,
	runID, jobID int64, step *models.PipelineStep, image, workDir string) (int, error) {

	now := time.Now().UTC()
	step.Status = "running"
	step.StartedAt = &now
	db.ID(step.ID).Cols("status", "started_at").Update(step) //nolint:errcheck

	cmd := exec.CommandContext(ctx, "docker", "run", "--rm",
		"-v", workDir+":/workspace",
		"-w", "/workspace",
		"--network=none", // no network by default; Phase 2C will add network scopes
		image,
		"/bin/sh", "-ec", step.RunCmd,
	)

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return 1, err
	}
	cmd.Stderr = cmd.Stdout // merge stderr into stdout

	if err := cmd.Start(); err != nil {
		return 1, fmt.Errorf("docker run: %w", err)
	}

	chunk := 0
	scanner := bufio.NewScanner(stdout)
	for scanner.Scan() {
		line := scanner.Text() + "\n"
		writeLogChunk(db, bus, runID, jobID, step.ID, chunk, line)
		chunk++
	}

	exitCode := 0
	if err := cmd.Wait(); err != nil {
		if exitErr, ok := err.(*exec.ExitError); ok {
			exitCode = exitErr.ExitCode()
		} else {
			exitCode = 1
		}
	}
	return exitCode, nil
}

// extractWorkspace uses git-archive to export the repo at a given SHA into a
// temporary directory under workspaceRoot.
func extractWorkspace(repoPath, sha, workspaceRoot string, runID int64) (string, error) {
	dir := filepath.Join(workspaceRoot, fmt.Sprintf("run-%d", runID))
	if err := os.MkdirAll(dir, 0755); err != nil {
		return "", err
	}

	archive := exec.Command("git", "archive", "--format=tar", sha)
	archive.Dir = repoPath
	archive.Env = []string{"GIT_TERMINAL_PROMPT=0", "HOME=/tmp"}

	tar := exec.Command("tar", "-x", "-C", dir)
	tar.Stdin, _ = archive.StdoutPipe()

	if err := archive.Start(); err != nil {
		os.RemoveAll(dir)
		return "", fmt.Errorf("git archive: %w", err)
	}
	if err := tar.Start(); err != nil {
		archive.Process.Kill() //nolint:errcheck
		os.RemoveAll(dir)
		return "", fmt.Errorf("tar: %w", err)
	}

	archiveErr := archive.Wait()
	tarErr := tar.Wait()
	if archiveErr != nil {
		os.RemoveAll(dir)
		return "", fmt.Errorf("git archive wait: %w", archiveErr)
	}
	if tarErr != nil {
		os.RemoveAll(dir)
		return "", fmt.Errorf("tar wait: %w", tarErr)
	}
	return dir, nil
}

func writeLogChunk(db *xorm.Engine, bus events.EventBus, runID, jobID, stepID int64, idx int, content string) {
	entry := &models.PipelineStepLog{
		StepID:     stepID,
		ChunkIndex: idx,
		Content:    content,
	}
	db.Insert(entry) //nolint:errcheck
	bus.Publish(events.SubjectPipelineLog, events.LogChunkEvent{ //nolint:errcheck
		RunID: runID, JobID: jobID, StepID: stepID, ChunkIndex: idx, Content: content,
	})
}

func markStep(db *xorm.Engine, step *models.PipelineStep, status string, exitCode int) {
	now := time.Now().UTC()
	step.Status = status
	step.ExitCode = exitCode
	step.FinishedAt = &now
	db.ID(step.ID).Cols("status", "exit_code", "finished_at").Update(step) //nolint:errcheck
}

func failJob(db *xorm.Engine, bus events.EventBus, jc JobContext, reason string) {
	now := time.Now().UTC()
	jc.Job.Status = "failed"
	jc.Job.FinishedAt = &now
	db.ID(jc.Job.ID).Cols("status", "finished_at").Update(&jc.Job) //nolint:errcheck

	// Write the failure reason as a synthetic log line.
	var lastStep models.PipelineStep
	if found, _ := db.Where("job_id = ?", jc.Job.ID).Desc("seq").Get(&lastStep); found {
		writeLogChunk(db, bus, jc.Run.ID, jc.Job.ID, lastStep.ID, 0,
			"\n[ForgeBucket] Job failed: "+reason+"\n")
	}

	bus.Publish(events.SubjectJobFailed, events.JobEvent{ //nolint:errcheck
		RunID: jc.Run.ID, JobID: jc.Job.ID, Status: "failed", At: now,
	})
}

// workspaceDir returns the scratch directory root for CI job workspaces.
func workspaceDir(artifactRoot string) string {
	return filepath.Join(filepath.Dir(artifactRoot), "ci-workspaces")
}

// IsDockerAvailable checks whether the docker CLI is reachable.
func IsDockerAvailable() bool {
	cmd := exec.Command("docker", "info")
	cmd.Env = []string{"HOME=/tmp"}
	return cmd.Run() == nil
}

// stepsForJob loads PipelineStep rows for a job ordered by seq.
func stepsForJob(db *xorm.Engine, jobID int64) ([]models.PipelineStep, error) {
	var steps []models.PipelineStep
	err := db.Where("job_id = ?", jobID).Asc("seq").Find(&steps)
	return steps, err
}

// repoForRun loads the Repository for a given run.
func repoForRun(db *xorm.Engine, runID int64) (models.Repository, models.PipelineRun, bool) {
	var run models.PipelineRun
	if found, _ := db.ID(runID).Get(&run); !found {
		return models.Repository{}, run, false
	}
	var repo models.Repository
	if found, _ := db.ID(run.RepoID).Get(&repo); !found {
		return models.Repository{}, run, false
	}
	return repo, run, true
}

// buildJobContext assembles a JobContext from DB rows.
func buildJobContext(db *xorm.Engine, jobID int64) (JobContext, bool) {
	var job models.PipelineJob
	if found, _ := db.ID(jobID).Get(&job); !found {
		return JobContext{}, false
	}
	repo, run, ok := repoForRun(db, job.RunID)
	if !ok {
		return JobContext{}, false
	}
	steps, err := stepsForJob(db, jobID)
	if err != nil {
		return JobContext{}, false
	}
	return JobContext{Run: run, Job: job, Steps: steps, Repo: repo}, true
}

// pipeForRun returns the longest-matching step label for an image.
// Phase 2B: unused placeholder for future label matching.
func pipeForRun(_ string) string { return "" }

// sanitizeImage prevents injection in docker image names.
func sanitizeImage(image string) string {
	// Allow only characters valid in Docker image references.
	var b strings.Builder
	for _, c := range image {
		if (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
			(c >= '0' && c <= '9') || c == '.' || c == '-' || c == '_' ||
			c == '/' || c == ':' || c == '@' {
			b.WriteRune(c)
		}
	}
	return b.String()
}