package pipeline

import (
	"context"
	"fmt"
	"net/http"
	"os"
	"strconv"
	"strings"
	"sync"

	"evobgp/internal/store"
)

func collectConcurrency() int {
	n := 8
	if s := strings.TrimSpace(os.Getenv("EVOBGP_COLLECT_CONCURRENCY")); s != "" {
		if v, err := strconv.Atoi(s); err == nil && v > 0 {
			n = v
		}
	}
	if n > 32 {
		n = 32
	}
	return n
}

// aggregateTenantPrefixRowsAll builds the union of materialized prefixes for all enabled modules.
// Uses per-module snapshots when inputs are unchanged to avoid duplicate external fetches on render.
func aggregateTenantPrefixRowsAll(ctx context.Context, st store.Backend, hc *http.Client, tenantID string) ([]store.PrefixRow, error) {
	mods := st.ListModules(tenantID)
	type modRef struct {
		id string
	}
	var enabled []modRef
	for _, m := range mods {
		if m != nil && m.Enabled {
			enabled = append(enabled, modRef{id: m.ID})
		}
	}
	if len(enabled) == 0 {
		return nil, nil
	}
	if len(enabled) == 1 {
		omod, err := st.GetModule(tenantID, enabled[0].id)
		if err != nil {
			return nil, err
		}
		return rowsForModule(ctx, st, hc, tenantID, omod)
	}

	sem := make(chan struct{}, collectConcurrency())
	results := make([][]store.PrefixRow, len(enabled))
	errs := make([]error, len(enabled))
	var wg sync.WaitGroup
	for i, ref := range enabled {
		wg.Add(1)
		go func(idx int, moduleID string) {
			defer wg.Done()
			sem <- struct{}{}
			defer func() { <-sem }()
			omod, err := st.GetModule(tenantID, moduleID)
			if err != nil {
				errs[idx] = err
				return
			}
			rows, err := rowsForModule(ctx, st, hc, tenantID, omod)
			if err != nil {
				errs[idx] = fmt.Errorf("module %s: %w", moduleID, err)
				return
			}
			results[idx] = rows
		}(i, ref.id)
	}
	wg.Wait()
	for _, err := range errs {
		if err != nil {
			return nil, err
		}
	}
	var out []store.PrefixRow
	for _, part := range results {
		out = append(out, part...)
	}
	return out, nil
}

func rowsForModule(ctx context.Context, st store.Backend, hc *http.Client, tenantID string, mod *store.Module) ([]store.PrefixRow, error) {
	if rows, ok, err := moduleRowsFromSnapshot(st, tenantID, mod); err != nil {
		return nil, err
	} else if ok {
		return rows, nil
	}
	var prior []store.PrefixRow
	if snap, ok, _ := st.GetModulePrefixSnapshot(tenantID, mod.ID); ok && snap != nil {
		prior = snap.Prefixes
	}
	rows, err := collectModulePrefixRows(ctx, st, hc, tenantID, mod, prior)
	if err != nil {
		return nil, err
	}
	if err := persistModuleSnapshot(st, tenantID, mod, rows); err != nil {
		return nil, err
	}
	return rows, nil
}