package api

import (
	"context"
	"encoding/json"
	"net/http"

	"github.com/docker/docker/api/types"
	"github.com/shcizo/package-updater/internal/discovery"
	"github.com/shcizo/package-updater/internal/logging"
	"github.com/shcizo/package-updater/internal/metrics"
	"github.com/shcizo/package-updater/internal/updater"
)

// Finder is the discovery interface used by the update handler.
type Finder interface {
	FindJobs(ctx context.Context, image string) ([]discovery.Job, error)
}

// Submitter is the queue interface used by the update handler.
type Submitter interface {
	Submit(ctx context.Context, jobs []discovery.Job) []updater.Result
}

// Pinger pings the Docker daemon for the healthcheck.
type Pinger interface {
	Ping(ctx context.Context) (types.Ping, error)
}

// Handlers wires the HTTP endpoints to the rest of the service.
type Handlers struct {
	finder    Finder
	submitter Submitter
	pinger    Pinger
	version   string
	commit    string
	buildTime string
	metrics   *metrics.Metrics
}

// NewHandlers constructs a Handlers value with all dependencies injected.
// m may be nil, in which case metrics recording is silently skipped.
func NewHandlers(f Finder, s Submitter, p Pinger, version, commit, buildTime string, m *metrics.Metrics) *Handlers {
	return &Handlers{finder: f, submitter: s, pinger: p, version: version, commit: commit, buildTime: buildTime, metrics: m}
}

// Update implements POST /update.
func (h *Handlers) Update(w http.ResponseWriter, r *http.Request) {
	var req UpdateRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSONError(w, http.StatusBadRequest, "invalid JSON body")
		return
	}
	if req.Image == "" {
		writeJSONError(w, http.StatusBadRequest, "image is required")
		return
	}

	jobs, err := h.finder.FindJobs(r.Context(), req.Image)
	if err != nil {
		writeJSONError(w, http.StatusInternalServerError, "discovery failed: "+err.Error())
		return
	}

	resp := UpdateResponse{
		RequestID: logging.RequestIDFrom(r.Context()),
		Image:     req.Image,
		Tag:       req.Tag,
		Matched:   len(jobs),
		Results:   []ResultDTO{},
	}

	if len(jobs) == 0 {
		writeJSON(w, http.StatusOK, resp)
		return
	}

	results := h.submitter.Submit(r.Context(), jobs)
	updated, failed := 0, 0
	for _, res := range results {
		composeFile := ""
		if len(res.Job.ConfigFiles) > 0 {
			composeFile = res.Job.ConfigFiles[0]
		}
		resp.Results = append(resp.Results, ResultDTO{
			Project:     res.Job.Project,
			Service:     res.Job.Service,
			ComposeFile: composeFile,
			Status:      string(res.Status),
			Error:       res.Error,
			DurationMs:  res.DurationMs,
		})
		if res.Status == updater.StatusUpdated {
			updated++
		} else {
			failed++
		}
	}

	switch {
	case failed == 0:
		writeJSON(w, http.StatusOK, resp)
	case updated == 0:
		writeJSON(w, http.StatusInternalServerError, resp)
	default:
		writeJSON(w, http.StatusMultiStatus, resp)
	}
}

// Healthz implements GET /healthz.
func (h *Handlers) Healthz(w http.ResponseWriter, r *http.Request) {
	if _, err := h.pinger.Ping(r.Context()); err != nil {
		if h.metrics != nil {
			h.metrics.DockerPingUp.Set(0)
		}
		writeJSON(w, http.StatusServiceUnavailable, HealthResponse{Status: "unhealthy", Docker: "unreachable"})
		return
	}
	if h.metrics != nil {
		h.metrics.DockerPingUp.Set(1)
	}
	writeJSON(w, http.StatusOK, HealthResponse{Status: "ok", Docker: "ok"})
}

// Version implements GET /version.
func (h *Handlers) Version(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, VersionResponse{
		Version:   h.version,
		Commit:    h.commit,
		BuildTime: h.buildTime,
	})
}

func writeJSON(w http.ResponseWriter, code int, body any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	_ = json.NewEncoder(w).Encode(body)
}

func writeJSONError(w http.ResponseWriter, code int, msg string) {
	writeJSON(w, code, map[string]string{"error": msg})
}