package http

import (
	"bufio"
	"encoding/json"
	"fmt"
	stdhttp "net/http"
	"strings"

	"github.com/go-chi/chi/v5"

	"gitea.dcglab.co.uk/steve/restic-manager/internal/store"
)

// handleJobLogDownload is GET /api/jobs/{id}/log{.txt,.ndjson}.
//
// Source of truth is the persisted job_logs table — works any time,
// regardless of whether the job is running or already finished. The
// download is "everything the server has up to right now"; the live
// stream is unaffected (no pause needed). If the operator wants a
// fuller snapshot of a still-running job, they hit Download again.
//
// Format is picked from the URL suffix (.txt | .ndjson) for a
// sensible filename in the browser, or the ?format= query param for
// REST callers. Default is txt.
func (s *Server) handleJobLogDownload(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	if _, ok := s.requireUser(r); !ok {
		writeJSONError(w, stdhttp.StatusUnauthorized, "unauthorised", "")
		return
	}
	jobID := chi.URLParam(r, "id")
	if jobID == "" {
		writeJSONError(w, stdhttp.StatusBadRequest, "missing_job_id", "")
		return
	}
	job, err := s.deps.Store.GetJob(r.Context(), jobID)
	if err != nil {
		writeJSONError(w, stdhttp.StatusNotFound, "job_not_found", "")
		return
	}

	format := r.URL.Query().Get("format")
	if format == "" {
		// Sniff the URL — chi routes both /log.txt and /log.ndjson here
		// (or .log if a future route adds it) via the {format} matcher.
		fmtParam := chi.URLParam(r, "format")
		switch fmtParam {
		case "ndjson":
			format = "ndjson"
		default:
			format = "txt"
		}
	}

	logs, err := s.deps.Store.ListJobLogs(r.Context(), jobID, 0, 0)
	if err != nil {
		writeJSONError(w, stdhttp.StatusInternalServerError, "internal", err.Error())
		return
	}

	short := jobID
	if len(short) > 8 {
		short = short[:8]
	}
	filename := "job-" + job.Kind + "-" + short
	switch format {
	case "ndjson":
		w.Header().Set("Content-Type", "application/x-ndjson; charset=utf-8")
		w.Header().Set("Content-Disposition",
			`attachment; filename="`+filename+`.ndjson"`)
		writeLogsNDJSON(w, logs)
	default:
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.Header().Set("Content-Disposition",
			`attachment; filename="`+filename+`.txt"`)
		writeLogsText(w, job, logs)
	}
}

// writeLogsText renders the logs in the same shape the live page shows:
// "HH:MM:SS.mmm  TAG  payload". Adds a small header so the file is
// useful as a standalone artefact (operator pastes it into a ticket).
func writeLogsText(w stdhttp.ResponseWriter, job *store.Job, logs []store.JobLogLine) {
	bw := bufio.NewWriter(w)
	defer func() { _ = bw.Flush() }()
	_, _ = fmt.Fprintf(bw, "# job %s · kind %s · status %s\n",
		job.ID, job.Kind, job.Status)
	if job.StartedAt != nil {
		_, _ = fmt.Fprintf(bw, "# started %s\n", job.StartedAt.UTC().Format("2006-01-02T15:04:05.000Z"))
	}
	if job.FinishedAt != nil {
		_, _ = fmt.Fprintf(bw, "# finished %s\n", job.FinishedAt.UTC().Format("2006-01-02T15:04:05.000Z"))
	}
	_, _ = fmt.Fprintf(bw, "# %d log lines\n\n", len(logs))
	for _, l := range logs {
		tag := streamTag(l.Stream)
		ts := l.TS.UTC().Format("15:04:05.000")
		// Strip embedded newlines from payload — log lines should be
		// single-line, but defensive: a stray '\n' in stderr would
		// break grep -n.
		payload := strings.ReplaceAll(l.Payload, "\n", " ")
		_, _ = fmt.Fprintf(bw, "%s  %s  %s\n", ts, tag, payload)
	}
}

// writeLogsNDJSON emits one JSON object per line. Each object stands
// alone — appending to the file remains valid NDJSON.
func writeLogsNDJSON(w stdhttp.ResponseWriter, logs []store.JobLogLine) {
	enc := json.NewEncoder(w)
	for _, l := range logs {
		_ = enc.Encode(struct {
			Seq     int64  `json:"seq"`
			TS      string `json:"ts"`
			Stream  string `json:"stream"`
			Payload string `json:"payload"`
		}{
			Seq:     l.Seq,
			TS:      l.TS.UTC().Format("2006-01-02T15:04:05.000Z"),
			Stream:  l.Stream,
			Payload: l.Payload,
		})
	}
}

func streamTag(s string) string {
	switch s {
	case "stdout":
		return "OUT"
	case "stderr":
		return "ERR"
	case "event":
		return "EVENT"
	}
	return strings.ToUpper(s)
}