package ci

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"

	"hearthforge/internal/config"
	"hearthforge/internal/db"
	"hearthforge/internal/gitcmd"
)

// ciMaxLogBytes caps the log stored per step.
const ciMaxLogBytes = 2 * 1024 * 1024

// TriggerOpts describes why a run starts and which commit it builds.
type TriggerOpts struct {
	// TriggerSource is "push", "tag" or "manual".
	TriggerSource     string
	CommitSha         string
	CommitBranch      string
	CommitTag         string
	TriggeredBy       int64
	VariableOverrides map[string]string
}

// task is one run that holds a concurrency slot.
type task struct {
	cancel      context.CancelFunc
	containerID string
}

// Runner owns the CI queue and talks to the container engine.
type Runner struct {
	cfg *config.Config
	db  *db.DB

	socketMu sync.Mutex
	socket   string
	client   *http.Client

	mu      sync.Mutex
	running map[int64]*task
	// queue holds run ids whose DB row is "queued". pumpQueue is the sole
	// writer of `running`, so the slot check and the reservation happen
	// together under one lock.
	queue []int64
}

func New(cfg *config.Config, database *db.DB) *Runner {
	return &Runner{cfg: cfg, db: database, running: map[int64]*task{}}
}

func (r *Runner) repoPath(name string) string {
	return filepath.Join(r.cfg.ReposDir(), name+".git")
}

// ErrNoConfig means the commit carries no .hearthforge-ci.toml. Callers tell
// it apart from a parse error to explain why CI cannot run.
var ErrNoConfig = errors.New(".hearthforge-ci.toml not found at commit")

// ConfigAt reads and parses .hearthforge-ci.toml at a commit or ref.
func (r *Runner) ConfigAt(ctx context.Context, repoName, ref string) (*Config, error) {
	cmd := exec.CommandContext(ctx, "git", "-C", r.repoPath(repoName), "show",
		"--end-of-options", ref+":.hearthforge-ci.toml")
	cmd.Env = gitcmd.Env()
	out, err := cmd.Output()
	if err != nil || len(out) == 0 {
		return nil, ErrNoConfig
	}
	return ParseCiConfig(string(out))
}

// --- Queue ---

// QueuePosition returns the 1-based place of a queued run, or 0.
func (r *Runner) QueuePosition(runID int64) int {
	r.mu.Lock()
	defer r.mu.Unlock()
	for i, id := range r.queue {
		if id == runID {
			return i + 1
		}
	}
	return 0
}

// enqueue puts a run in the queue and starts it when a slot is free.
// The row is flipped to "queued" under the same lock that decides there is no
// slot, so two triggers that arrive together cannot both stay "pending".
func (r *Runner) enqueue(ctx context.Context, runID int64) {
	r.mu.Lock()
	r.queue = append(r.queue, runID)
	if len(r.running)+len(r.queue) > r.cfg.CIMaxConcurrent {
		// pumpQueue is the only starter and it needs the same lock, so this
		// update cannot clobber a row that just went running.
		r.execSQL(ctx, `UPDATE ci_runs SET status = 'queued' WHERE id = ?`, runID)
	}
	r.mu.Unlock()
	r.pumpQueue()
}

func (r *Runner) pumpQueue() {
	for {
		r.mu.Lock()
		if len(r.queue) == 0 || len(r.running) >= r.cfg.CIMaxConcurrent {
			r.mu.Unlock()
			return
		}
		runID := r.queue[0]
		r.queue = r.queue[1:]
		// The run outlives the request that created it, so it gets its own
		// context. CancelRun cancels it.
		ctx, cancel := context.WithCancel(context.Background())
		t := &task{cancel: cancel}
		r.running[runID] = t
		r.mu.Unlock()

		go r.spawnRun(ctx, runID, t)
	}
}

// spawnRun promotes the row to pending, runs it, and reconciles the row when
// executeRun itself fails.
func (r *Runner) spawnRun(ctx context.Context, runID int64, t *task) {
	defer func() {
		if rec := recover(); rec != nil {
			log.Printf("[ci] run %d panicked: %v", runID, rec)
			r.finishSlot(runID, t)
			r.execSQL(context.Background(),
				`UPDATE ci_runs SET status = 'failure', finished_at = ?
				 WHERE id = ? AND status IN ('pending','running','queued')`, db.NowISO(), runID)
			r.pumpQueue()
		}
	}()
	// Promote queued→pending before executing, so executeRun's failure path
	// (which only matches pending/running/queued) can mark it failed.
	r.execSQL(ctx, `UPDATE ci_runs SET status = 'pending' WHERE id = ?`, runID)
	r.executeRun(ctx, runID, t)
}

// finishSlot releases the run's concurrency slot. It only drops the slot this
// execution owns: a retry that started the same run again holds a different
// task, and deleting that one would leak its slot forever.
func (r *Runner) finishSlot(runID int64, t *task) {
	r.mu.Lock()
	if r.running[runID] == t {
		delete(r.running, runID)
	}
	r.mu.Unlock()
}

func (r *Runner) setContainer(t *task, containerID string) {
	r.mu.Lock()
	t.containerID = containerID
	r.mu.Unlock()
}

// --- Small DB helpers ---

func (r *Runner) execSQL(ctx context.Context, query string, args ...any) {
	if _, err := r.db.ExecContext(ctx, query, args...); err != nil {
		log.Printf("[ci] sql failed: %v", err)
	}
}

func (r *Runner) insertStep(ctx context.Context, runID int64, name, status string, started bool) int64 {
	var startedAt any
	if started {
		startedAt = db.NowISO()
	}
	res, err := r.db.ExecContext(ctx,
		`INSERT INTO ci_steps (run_id, name, status, started_at) VALUES (?, ?, ?, ?)`,
		runID, name, status, startedAt)
	if err != nil {
		log.Printf("[ci] insert step failed: %v", err)
		return 0
	}
	id, _ := res.LastInsertId()
	return id
}

// --- Public API ---

// TriggerRun records a run and starts it, or queues it when every slot is
// taken. It returns the run id.
func (r *Runner) TriggerRun(ctx context.Context, repoName string, opts TriggerOpts) (int64, error) {
	var repoID int64
	err := r.db.QueryRowContext(ctx, `SELECT id FROM repositories WHERE name = ?`, repoName).Scan(&repoID)
	if err != nil {
		return 0, errors.New("repository not found")
	}

	var overrides any
	if len(opts.VariableOverrides) > 0 {
		buf, err := json.Marshal(opts.VariableOverrides)
		if err != nil {
			return 0, err
		}
		overrides = string(buf)
	}
	var triggeredBy any
	if opts.TriggeredBy > 0 {
		triggeredBy = opts.TriggeredBy
	}
	res, err := r.db.ExecContext(ctx,
		`INSERT INTO ci_runs (repo_id, triggered_by, trigger_source, commit_sha,
		    commit_branch, commit_tag, status, variable_overrides)
		 VALUES (?, ?, ?, ?, ?, ?, 'pending', ?)`,
		repoID, triggeredBy, opts.TriggerSource, opts.CommitSha,
		nullString(opts.CommitBranch), nullString(opts.CommitTag), overrides)
	if err != nil {
		return 0, err
	}
	runID, err := res.LastInsertId()
	if err != nil {
		return 0, err
	}

	// The human-facing run number comes from a per-repo counter. One
	// upsert-and-increment cannot collide under concurrent triggers, and it
	// never reuses a number after pruneHistory shrinks the table.
	var repoRunID int64
	err = r.db.QueryRowContext(ctx,
		`INSERT INTO ci_run_counters (repo_id, last_run_id) VALUES (?, 1)
		 ON CONFLICT(repo_id) DO UPDATE SET last_run_id = last_run_id + 1
		 RETURNING last_run_id`, repoID).Scan(&repoRunID)
	if err != nil {
		return 0, err
	}
	r.execSQL(ctx, `UPDATE ci_runs SET repo_run_id = ? WHERE id = ?`, repoRunID, runID)

	r.enqueue(ctx, runID)
	return runID, nil
}

// ErrRunNotFinished is returned when a retry targets a run that is still
// queued or executing.
var ErrRunNotFinished = errors.New("run is not finished")

// RetryRun clears a finished run's steps and artifacts and runs it again.
// The reset only applies to a run in a terminal status, so a retry cannot
// hijack a run that is still executing.
func (r *Runner) RetryRun(ctx context.Context, runID, retriedBy int64) error {
	var repoID int64
	if err := r.db.QueryRowContext(ctx, `SELECT repo_id FROM ci_runs WHERE id = ?`, runID).Scan(&repoID); err != nil {
		return errors.New("run not found")
	}
	res, err := r.db.ExecContext(ctx,
		`UPDATE ci_runs SET status = 'pending', triggered_by = ?, started_at = NULL, finished_at = NULL
		 WHERE id = ? AND status IN ('success','failure','warning','cancelled','skipped')`,
		retriedBy, runID)
	if err != nil {
		return err
	}
	if n, err := res.RowsAffected(); err != nil {
		return err
	} else if n == 0 {
		return ErrRunNotFinished
	}
	r.execSQL(ctx, `DELETE FROM ci_steps WHERE run_id = ?`, runID)
	os.RemoveAll(r.artifactDir(runID))
	r.execSQL(ctx, `DELETE FROM ci_artifacts WHERE run_id = ?`, runID)
	r.enqueue(ctx, runID)
	return nil
}

// CancelRun stops a running or queued run.
func (r *Runner) CancelRun(ctx context.Context, runID int64) error {
	r.mu.Lock()
	t := r.running[runID]
	var containerID string
	if t != nil {
		containerID = t.containerID
	}
	for i, id := range r.queue {
		if id == runID {
			r.queue = append(r.queue[:i], r.queue[i+1:]...)
			break
		}
	}
	r.mu.Unlock()

	if t != nil {
		t.cancel()
		if containerID != "" {
			// Docker has no per-exec kill, so removing the container is what
			// stops the command running inside it.
			r.removeContainer(ctx, containerID)
		}
	}
	r.execSQL(ctx,
		`UPDATE ci_runs SET status = 'cancelled', finished_at = ?
		 WHERE id = ? AND status IN ('pending','running','queued')`, db.NowISO(), runID)
	return nil
}

// PurgeRepoCaches deletes this repo's cache volumes and returns how many
// went. It fails when the engine is unreachable.
func (r *Runner) PurgeRepoCaches(ctx context.Context, repoName string) (int, error) {
	names, err := r.listRepoVolumes(ctx, repoName)
	if err != nil {
		return 0, err
	}
	removed := 0
	for _, name := range names {
		if r.removeVolume(ctx, name) {
			removed++
		}
	}
	return removed, nil
}

// CancelStaleRuns cleans up runs a restart interrupted. Their containers are
// force-removed and the rows read "cancelled", so they can be retried.
func (r *Runner) CancelStaleRuns(ctx context.Context) error {
	rows, err := r.db.QueryContext(ctx,
		`SELECT id FROM ci_runs WHERE status IN ('pending','running','queued')`)
	if err != nil {
		return err
	}
	var ids []int64
	for rows.Next() {
		var id int64
		if err := rows.Scan(&id); err != nil {
			rows.Close()
			return err
		}
		ids = append(ids, id)
	}
	rows.Close()
	if err := rows.Err(); err != nil {
		return err
	}
	for _, id := range ids {
		r.removeContainer(ctx, containerName(id))
	}
	now := db.NowISO()
	r.execSQL(ctx, `UPDATE ci_runs SET status = 'cancelled', finished_at = ?
		 WHERE status IN ('pending','running','queued')`, now)
	r.execSQL(ctx, `UPDATE ci_steps SET status = 'cancelled', finished_at = ?, log = 'Skipped: run was cancelled'
		 WHERE status IN ('pending','running')`, now)
	return nil
}

func (r *Runner) artifactDir(runID int64) string {
	return filepath.Join(r.cfg.CIArtifactsDir(), strconv.FormatInt(runID, 10))
}

// pruneHistory keeps only the newest CI_MAX_HISTORY runs of a repository.
func (r *Runner) pruneHistory(ctx context.Context, repoID int64) {
	// Active runs never get pruned: their row is what the queue and the
	// finish path update.
	rows, err := r.db.QueryContext(ctx,
		`SELECT id FROM ci_runs WHERE repo_id = ?
		   AND status NOT IN ('pending','running','queued') ORDER BY id DESC`, repoID)
	if err != nil {
		return
	}
	var ids []int64
	for rows.Next() {
		var id int64
		if rows.Scan(&id) == nil {
			ids = append(ids, id)
		}
	}
	rows.Close()
	if len(ids) <= r.cfg.CIMaxHistory {
		return
	}
	toDelete := ids[r.cfg.CIMaxHistory:]
	args := make([]any, len(toDelete))
	for i, id := range toDelete {
		os.RemoveAll(r.artifactDir(id))
		args[i] = id
	}
	placeholders := strings.TrimSuffix(strings.Repeat("?,", len(args)), ",")
	r.execSQL(ctx, `DELETE FROM ci_runs WHERE id IN (`+placeholders+`)`, args...)
}

// --- Environment ---

// buildEnvVars assembles the container environment. Later sources win on a
// name clash: config defaults, then manual overrides, then secrets.
func buildEnvVars(runID int64, repoName, baseURL, host string, run runRow, cfg *Config,
	overrides map[string]string, secrets []secret,
) (envArray, secretValues []string) {
	order := []string{}
	vars := map[string]string{}
	set := func(k, v string) {
		if _, seen := vars[k]; !seen {
			order = append(order, k)
		}
		vars[k] = v
	}

	refName := run.CommitTag
	if refName == "" {
		refName = run.CommitBranch
	}
	shortSha := run.CommitSha
	if len(shortSha) > 8 {
		shortSha = shortSha[:8]
	}
	set("CI", "true")
	set("CI_PIPELINE_ID", strconv.FormatInt(runID, 10))
	set("CI_REPO_NAME", repoName)
	set("CI_SERVER_URL", baseURL)
	set("CI_TRIGGER_SOURCE", run.TriggerSource)
	set("CI_COMMIT_SHA", run.CommitSha)
	set("CI_COMMIT_SHORT_SHA", shortSha)
	set("CI_COMMIT_BRANCH", run.CommitBranch)
	set("CI_COMMIT_TAG", run.CommitTag)
	set("CI_COMMIT_REF_NAME", refName)
	set("CI_REGISTRY", host+"/"+repoName)

	for _, name := range cfg.VariableOrder {
		if def, ok := cfg.Variables[name]; ok && def.Default != "" {
			set(name, def.Default)
		}
	}
	names := make([]string, 0, len(overrides))
	for name := range overrides {
		names = append(names, name)
	}
	sort.Strings(names)
	for _, name := range names {
		set(name, overrides[name])
	}
	for _, s := range secrets {
		set(s.name, s.value)
		secretValues = append(secretValues, s.value)
	}

	for _, k := range order {
		envArray = append(envArray, k+"="+vars[k])
	}
	return envArray, secretValues
}

// maskSecrets replaces secret values in a log. It is a plain text match: a
// secret printed in encoded or split form is not caught.
func maskSecrets(text string, secrets []string) string {
	for _, s := range secrets {
		if s != "" {
			text = strings.ReplaceAll(text, s, "[MASKED]")
		}
	}
	return text
}

type secret struct{ name, value string }

type runRow struct {
	RepoID        int64
	TriggerSource string
	CommitSha     string
	CommitBranch  string
	CommitTag     string
	Overrides     string
}

func nullString(s string) any {
	if s == "" {
		return nil
	}
	return s
}

func (r *Runner) loadRun(ctx context.Context, runID int64) (runRow, error) {
	var row runRow
	var sha, branch, tag, overrides sql.NullString
	err := r.db.QueryRowContext(ctx,
		`SELECT repo_id, trigger_source, commit_sha, commit_branch, commit_tag, variable_overrides
		 FROM ci_runs WHERE id = ?`, runID).
		Scan(&row.RepoID, &row.TriggerSource, &sha, &branch, &tag, &overrides)
	if err != nil {
		return row, errors.New("run not found")
	}
	row.CommitSha, row.CommitBranch = sha.String, branch.String
	row.CommitTag, row.Overrides = tag.String, overrides.String
	return row, nil
}

// --- Checkout upload ---

// uploadCheckout puts the commit's tree into the container at destPath.
//
// The checkout deliberately does not happen inside the container: that would
// force every CI image to carry git. It is not a bind mount either, because
// the daemon resolves bind sources in the host filesystem.
//
// `git archive` writes uid 0 and mode 0644/0755 into the tar headers, and no
// entry for the archive root, so the destination keeps the ownership the
// container gave it. No .git reaches the container.
func (r *Runner) uploadCheckout(ctx context.Context, containerID, repoName, commitSha, destPath string) error {
	// The archive carries destPath as its prefix and is extracted at /, so
	// the engine creates the directories and the image needs no mkdir.
	prefix := strings.TrimPrefix(path.Clean(destPath), "/") + "/"
	// --end-of-options: commit_sha is unvalidated text from the push.
	cmd := exec.CommandContext(ctx, "git", "-C", r.repoPath(repoName), "archive",
		"--format=tar", "--prefix="+prefix, "--end-of-options", commitSha)
	cmd.Env = gitcmd.Env()
	var stderr strings.Builder
	cmd.Stderr = &stderr
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return err
	}
	if err := cmd.Start(); err != nil {
		return err
	}
	resp, body, putErr := r.putArchive(ctx, containerID, "/", stdout)
	// The PUT stopped reading, so git would block writing into a full pipe.
	stdout.Close()
	waitErr := cmd.Wait()

	if putErr != nil {
		return putErr
	}
	if resp.StatusCode >= 300 {
		return fmt.Errorf("failed to upload the checkout: HTTP %d %s",
			resp.StatusCode, strings.TrimSpace(string(body)))
	}
	if waitErr != nil {
		return fmt.Errorf("failed to read %s: git archive failed %v %s",
			commitSha, waitErr, strings.TrimSpace(stderr.String()))
	}
	return nil
}

// --- Artifacts ---

// collectArtifacts copies this step's published files out of the container.
// Archives are built on the host from the engine's tar stream, so the image
// needs no archive tools.
func (r *Runner) collectArtifacts(ctx context.Context, runID int64, containerID string, step Step) {
	dir := r.artifactDir(runID)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return
	}

	// store streams the container file straight into the artifact directory.
	store := func(filename, srcPath string) {
		dest := filepath.Join(dir, filename)
		// The run directory is shared by every step. A second file of the
		// same name would overwrite the first and still add a row.
		if _, err := os.Stat(dest); err == nil {
			log.Printf("[ci] run %d: artifact %s already published, skipping %s", runID, filename, srcPath)
			return
		}
		size, err := r.copyFileFromContainer(ctx, containerID, srcPath, dest)
		if err != nil {
			log.Printf("[ci] run %d: artifact %s: %v", runID, srcPath, err)
			return
		}
		r.execSQL(ctx, `INSERT INTO ci_artifacts (run_id, filename, size) VALUES (?, ?, ?)`,
			runID, filename, size)
	}

	for _, srcPath := range step.PublishFile {
		store(path.Base(srcPath), srcPath)
	}

	for _, f := range archiveFormats {
		for _, srcPath := range f.pick(step) {
			filename := path.Base(srcPath) + f.ext
			dest := filepath.Join(dir, filename)
			if _, err := os.Stat(dest); err == nil {
				log.Printf("[ci] run %d: artifact %s already published, skipping %s", runID, filename, srcPath)
				continue
			}
			size, err := r.storeArchive(ctx, containerID, srcPath, dest, f.ext, r.cfg.CIMaxArtifactBytes)
			if err != nil {
				log.Printf("[ci] run %d: artifact %s: %v", runID, srcPath, err)
				continue
			}
			r.execSQL(ctx, `INSERT INTO ci_artifacts (run_id, filename, size) VALUES (?, ?, ?)`,
				runID, filename, size)
		}
	}
}