package api

import (
	"context"
	"net/http"
	"runtime"
	"time"

	"predictor-refactored/internal/datasets"
	apirest "predictor-refactored/pkg/rest"
)

// ListDatasets implements GET /api/v1/admin/datasets.
func (h *Handler) ListDatasets(_ context.Context) (*apirest.DatasetList, error) {
	stored, err := h.mgr.ListEpochs()
	if err != nil {
		return nil, apiError(http.StatusInternalServerError, err.Error())
	}
	loaded := make(map[string]datasets.LoadedDatasetInfo)
	for _, ld := range h.mgr.LoadedDatasets() {
		loaded[ld.ID.Filename()] = ld
	}

	out := &apirest.DatasetList{Source: h.mgr.Source(), Datasets: make([]apirest.DatasetEntry, 0, len(stored))}
	for _, id := range stored {
		entry := apirest.DatasetEntry{
			Filename: id.Filename(),
			Epoch:    id.Epoch.UTC(),
		}
		if !id.Subset.IsGlobal() {
			entry.Subset = apirest.NewOptSubsetSpec(subsetToAPI(id.Subset))
		}
		if ld, ok := loaded[id.Filename()]; ok {
			entry.Loaded = true
			entry.Coverage = apirest.NewOptCoverage(coverageToAPI(ld.Coverage))
		}
		out.Datasets = append(out.Datasets, entry)
	}
	return out, nil
}

// TriggerDatasetDownload implements POST /api/v1/admin/datasets.
func (h *Handler) TriggerDatasetDownload(ctx context.Context, req *apirest.DownloadRequest) (*apirest.DownloadAccepted, error) {
	if req.Latest.Or(false) {
		dctx, cancel := context.WithTimeout(ctx, 30*time.Second)
		defer cancel()
		jobID, err := h.mgr.Refresh(dctx, 0)
		if err != nil {
			return nil, apiError(http.StatusInternalServerError, err.Error())
		}
		return &apirest.DownloadAccepted{JobID: jobID}, nil
	}

	epoch, ok := req.Epoch.Get()
	if !ok {
		return nil, apiError(http.StatusBadRequest, "specify either epoch or latest=true")
	}
	id := datasets.DatasetID{Epoch: epoch.UTC()}
	if s, ok := req.Subset.Get(); ok {
		id.Subset = subsetFromAPI(s)
	}
	return &apirest.DownloadAccepted{JobID: h.mgr.Download(id)}, nil
}

// DeleteDataset implements DELETE /api/v1/admin/datasets/{name}.
func (h *Handler) DeleteDataset(_ context.Context, params apirest.DeleteDatasetParams) error {
	stored, err := h.mgr.ListEpochs()
	if err != nil {
		return apiError(http.StatusInternalServerError, err.Error())
	}
	for _, id := range stored {
		if id.Filename() == params.Name {
			if err := h.mgr.Remove(id); err != nil {
				return apiError(http.StatusInternalServerError, err.Error())
			}
			return nil
		}
	}
	return apiError(http.StatusNotFound, "dataset not found")
}

// ListDatasetJobs implements GET /api/v1/admin/jobs.
func (h *Handler) ListDatasetJobs(_ context.Context) ([]apirest.DownloadJob, error) {
	jobs := h.mgr.ListJobs()
	out := make([]apirest.DownloadJob, 0, len(jobs))
	for _, j := range jobs {
		out = append(out, downloadJobToAPI(j))
	}
	return out, nil
}

// GetDatasetJob implements GET /api/v1/admin/jobs/{id}.
func (h *Handler) GetDatasetJob(_ context.Context, params apirest.GetDatasetJobParams) (*apirest.DownloadJob, error) {
	j, ok := h.mgr.GetJob(params.ID)
	if !ok {
		return nil, apiError(http.StatusNotFound, "job not found")
	}
	dto := downloadJobToAPI(j)
	return &dto, nil
}

// CancelDatasetJob implements DELETE /api/v1/admin/jobs/{id}.
func (h *Handler) CancelDatasetJob(_ context.Context, params apirest.CancelDatasetJobParams) error {
	if !h.mgr.CancelJob(params.ID) {
		return apiError(http.StatusConflict, "job not found or already terminal")
	}
	return nil
}

// GetServiceStatus implements GET /api/v1/admin/status.
func (h *Handler) GetServiceStatus(_ context.Context) (*apirest.StatusResponse, error) {
	jobs := h.mgr.ListJobs()
	stored, _ := h.mgr.ListEpochs()
	loaded := h.mgr.LoadedDatasets()

	byStatus := apirest.StatusResponseJobsByStatus{}
	for _, j := range jobs {
		byStatus[string(j.Status)]++
	}
	var mem runtime.MemStats
	runtime.ReadMemStats(&mem)

	return &apirest.StatusResponse{
		Source:         h.mgr.Source(),
		Uptime:         time.Since(h.started).Round(time.Second).String(),
		Goroutines:     runtime.NumGoroutine(),
		MemoryMB:       int64(mem.Alloc / 1024 / 1024),
		JobsByStatus:   byStatus,
		StoredDatasets: len(stored),
		LoadedDatasets: len(loaded),
	}, nil
}

// --- dataset mapping helpers ----------------------------------------------

func downloadJobToAPI(j datasets.JobInfo) apirest.DownloadJob {
	dto := apirest.DownloadJob{
		ID:         j.ID,
		Source:     j.Source,
		Dataset:    j.Dataset.Filename(),
		Epoch:      j.Dataset.Epoch.UTC(),
		Status:     apirest.DownloadJobStatus(j.Status),
		StartedAt:  j.StartedAt.UTC(),
		TotalUnits: j.Total,
		DoneUnits:  j.Done,
		Bytes:      j.Bytes,
	}
	if j.EndedAt != nil {
		dto.EndedAt = apirest.NewOptDateTime(j.EndedAt.UTC())
	}
	if j.Err != "" {
		dto.Error = apirest.NewOptString(j.Err)
	}
	return dto
}

func subsetToAPI(s datasets.SubsetSpec) apirest.SubsetSpec {
	out := apirest.SubsetSpec{Members: s.Members}
	if s.Region != nil {
		out.Region = apirest.NewOptRegion(regionToAPI(*s.Region))
	}
	if s.HourRange != nil {
		out.HourRange = apirest.NewOptHourRange(apirest.HourRange{MinHour: s.HourRange.MinHour, MaxHour: s.HourRange.MaxHour})
	}
	return out
}

func subsetFromAPI(s apirest.SubsetSpec) datasets.SubsetSpec {
	out := datasets.SubsetSpec{Members: s.Members}
	if r, ok := s.Region.Get(); ok {
		out.Region = &datasets.Region{MinLat: r.MinLat, MaxLat: r.MaxLat, MinLng: r.MinLng, MaxLng: r.MaxLng}
	}
	if hr, ok := s.HourRange.Get(); ok {
		out.HourRange = &datasets.HourRange{MinHour: hr.MinHour, MaxHour: hr.MaxHour}
	}
	return out
}

func regionToAPI(r datasets.Region) apirest.Region {
	return apirest.Region{MinLat: r.MinLat, MaxLat: r.MaxLat, MinLng: r.MinLng, MaxLng: r.MaxLng}
}

func coverageToAPI(c datasets.Coverage) apirest.Coverage {
	return apirest.Coverage{
		Region:    regionToAPI(c.Region),
		StartTime: c.StartTime.UTC(),
		EndTime:   c.EndTime.UTC(),
	}
}