// bench runs the corridor stop-optimization benchmark (bench/tasks.json)
// against a router backend. It is the acceptance test for the
// "search along the route" primitives: route, stop_cost, optimize_stops.
//
// Usage:
//
//	bench [--tasks bench/tasks.json] [--record]
//
// --record writes observed golden values (direct route minutes and
// optimized orders) back into the tasks file for regression use.
package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"math"
	"os"
	"strings"
	"time"

	"maps/router/internal/geo"
	"maps/router/internal/plan"
	"maps/router/internal/route"
)

type Place struct {
	Name string  `json:"name"`
	Lat  float64 `json:"lat"`
	Lon  float64 `json:"lon"`
}

func (p Place) Point() geo.Point { return geo.Point{Lat: p.Lat, Lon: p.Lon} }

type Candidate struct {
	ID       string  `json:"id"`
	Name     string  `json:"name"`
	Lat      float64 `json:"lat"`
	Lon      float64 `json:"lon"`
	DwellMin int     `json:"dwellMin"`
}

type Check struct {
	Type             string   `json:"type"`
	ID               string   `json:"id"`
	Name             string   `json:"name"`
	Lat, Lon         float64  `json:",omitempty"`
	MinDistKm        float64  `json:"minDistKm,omitempty"`
	Candidate        string   `json:"candidate,omitempty"`
	MaxDetourMin     int      `json:"maxDetourMin,omitempty"`
	MinDetourMin     int      `json:"minDetourMin,omitempty"`
	MaxPct           float64  `json:"maxPct,omitempty"`
	GoldMin         float64  `json:"goldMin,omitempty"`
	GoldMax         float64  `json:"goldMax,omitempty"`
	Want             []string `json:"want,omitempty"`
}

type Task struct {
	ID         string      `json:"id"`
	Desc       string      `json:"desc"`
	Origin     Place       `json:"origin"`
	Dest       Place       `json:"dest"`
	K          int         `json:"k"`
	BudgetMin  int         `json:"budgetMin"`
	Candidates []Candidate `json:"candidates"`
	Checks     []Check     `json:"checks"`
}

type BenchFile struct {
	Backend     string `json:"backend"`
	ValhallaURL string `json:"valhalla_url"`
	Tasks       []Task `json:"tasks"`
}

type result struct {
	check  string
	status string // PASS FAIL RECORD
	detail string
}

func main() {
	tasksPath := flag.String("tasks", "bench/tasks.json", "path to tasks.json")
	record := flag.Bool("record", false, "record golden values into the tasks file")
	flag.Parse()

	raw, err := os.ReadFile(*tasksPath)
	if err != nil {
		fatal(err)
	}
	var bf BenchFile
	if err := json.Unmarshal(raw, &bf); err != nil {
		fatal(err)
	}
	var r route.Router
	switch bf.Backend {
	case "valhalla":
		r = route.NewValhalla(bf.ValhallaURL)
	case "osrm":
		r = route.NewOSRM("http://localhost:5000")
	default:
		fatal(fmt.Errorf("unknown backend %q", bf.Backend))
	}
	ctx := context.Background()
	delay := 150 * time.Millisecond
	if _, ok := r.(*route.OSRM); ok {
		delay = 0
	}

	failures := 0
	for ti := range bf.Tasks {
		t := &bf.Tasks[ti]
		fmt.Printf("=== %s: %s -> %s (k=%d)\n", t.ID, t.Origin.Name, t.Dest.Name, t.K)
		fmt.Printf("    %s\n", t.Desc)

		// Direct route (golden + corridor source).
		direct, err := r.Route(ctx, route.ProfileDrive, []geo.Point{t.Origin.Point(), t.Dest.Point()})
		if err != nil {
			fatal(fmt.Errorf("task %s: direct route: %w", t.ID, err))
		}
		fmt.Printf("    direct: %s (%.1f km)\n", fmtDur(direct.Duration), direct.Distance/1000)

		// Matrix over [candidates..., origin, dest].
		pts := make([]geo.Point, 0, len(t.Candidates)+2)
		for _, c := range t.Candidates {
			pts = append(pts, geo.Point{Lat: c.Lat, Lon: c.Lon})
		}
		pts = append(pts, t.Origin.Point(), t.Dest.Point())
		fmt.Printf("    building %dx%d matrix (%d calls)...\n", len(pts), len(pts), len(pts)*(len(pts)-1))
		t0 := time.Now()
		m, err := route.BuildMatrix(ctx, r, route.ProfileDrive, pts, delay)
		if err != nil {
			fatal(fmt.Errorf("task %s: matrix: %w", t.ID, err))
		}
		fmt.Printf("    matrix done in %s\n", time.Since(t0).Round(time.Second))

		stops := make([]plan.Stop, len(t.Candidates))
		for i, c := range t.Candidates {
			stops[i] = plan.Stop{ID: c.ID, Name: c.Name, At: geo.Point{Lat: c.Lat, Lon: c.Lon}, DwellMin: c.DwellMin}
		}

		candByID := map[string]plan.Stop{}
		for _, s := range stops {
			candByID[s.ID] = s
		}

		opt := plan.OptimizeStops(m, stops, t.K, t.BudgetMin)
		optNames := make([]string, len(opt.Order))
		for i, si := range opt.Order {
			optNames[i] = stops[si].ID
		}
		fmt.Printf("    optimized: %s (detour %d min, total %d min, exhaustive=%v)\n",
			strings.Join(optNames, " -> "), opt.DetourMin, opt.TotalMin, opt.Exhaustive)

		for ci := range t.Checks {
			ck := &t.Checks[ci]
			res := runCheck(ctx, r, t, m, stops, direct, opt, *ck)
			if res.status == "FAIL" {
				failures++
			}
			fmt.Printf("    [%s] %-22s %s\n", res.status, ck.ID, res.detail)
			if *record {
				applyRecord(ck, direct, optNames)
			}
		}
	}

	if *record {
		out, _ := json.MarshalIndent(bf, "", "  ")
		if err := os.WriteFile(*tasksPath, out, 0o644); err != nil {
			fatal(err)
		}
		fmt.Printf("\nrecorded goldens into %s\n", *tasksPath)
	}
	fmt.Printf("\n%s (%d failures)\n", outcome(failures), failures)
	if failures > 0 {
		os.Exit(1)
	}
}

func runCheck(ctx context.Context, r route.Router, t *Task, m route.Matrix, stops []plan.Stop,
	direct *route.Route, opt plan.OptimizeResult, ck Check) result {
	res := result{check: ck.ID}
	switch ck.Type {
	case "golden_route_min":
		mins := direct.Duration / 60
		if ck.GoldMin == 0 && ck.GoldMax == 0 {
			res.status = "RECORD"
			res.detail = fmt.Sprintf("direct = %.0f min (no golden yet, run --record)", mins)
			return res
		}
		lo, hi := ck.GoldMin, ck.GoldMax
		if lo == 0 {
			lo = mins - math.Inf(1)
		}
		if hi == 0 {
			hi = math.Inf(1)
		}
		if mins < lo || mins > hi {
			res.status = "FAIL"
			res.detail = fmt.Sprintf("direct = %.0f min, golden [%v, %v]", mins, lo, hi)
		} else {
			res.status = "PASS"
			res.detail = fmt.Sprintf("direct = %.0f min in [%v, %v]", mins, lo, hi)
		}

	case "route_avoids":
		p := geo.Point{Lat: ck.Lat, Lon: ck.Lon}
		dist := distFromRoute(direct, p)
		if dist < ck.MinDistKm*1000 {
			res.status = "FAIL"
			res.detail = fmt.Sprintf("%s: route comes within %.1f km (< %.0f km)", ck.Name, dist/1000, ck.MinDistKm)
		} else {
			res.status = "PASS"
			res.detail = fmt.Sprintf("%s: route stays %.0f km away (min %.0f)", ck.Name, dist/1000, ck.MinDistKm)
		}

	case "stop_free":
		c, ok := stopIdx(stops, ck.Candidate)
		if !ok {
			res.status, res.detail = "FAIL", "unknown candidate"
			return res
		}
		cost := plan.StopCost(m, c, stops[c])
		if cost.DetourMin > ck.MaxDetourMin {
			res.status = "FAIL"
			res.detail = fmt.Sprintf("detour = %d min > %d min cap", cost.DetourMin, ck.MaxDetourMin)
		} else {
			res.status = "PASS"
			res.detail = fmt.Sprintf("detour = %d min <= %d min", cost.DetourMin, ck.MaxDetourMin)
		}

	case "stop_detour_at_least":
		c, ok := stopIdx(stops, ck.Candidate)
		if !ok {
			res.status, res.detail = "FAIL", "unknown candidate"
			return res
		}
		cost := plan.StopCost(m, c, stops[c])
		if cost.DetourMin < ck.MinDetourMin {
			res.status = "FAIL"
			res.detail = fmt.Sprintf("detour = %d min < %d min floor", cost.DetourMin, ck.MinDetourMin)
		} else {
			res.status = "PASS"
			res.detail = fmt.Sprintf("detour = %d min >= %d min", cost.DetourMin, ck.MinDetourMin)
		}

	case "stop_detour_band":
		// The computed detour must fall in [min, max] — a regression
		// guard on corridor shape (router/extract changes would show here).
		c, ok := stopIdx(stops, ck.Candidate)
		if !ok {
			res.status, res.detail = "FAIL", "unknown candidate"
			return res
		}
		cost := plan.StopCost(m, c, stops[c])
		if cost.DetourMin < ck.MinDetourMin || cost.DetourMin > ck.MaxDetourMin {
			res.status = "FAIL"
			res.detail = fmt.Sprintf("detour = %d min outside [%d, %d]", cost.DetourMin, ck.MinDetourMin, ck.MaxDetourMin)
		} else {
			res.status = "PASS"
			res.detail = fmt.Sprintf("detour = %d min in [%d, %d]", cost.DetourMin, ck.MinDetourMin, ck.MaxDetourMin)
		}

	case "optimize_order":
		got := make([]string, len(opt.Order))
		for i, si := range opt.Order {
			got[i] = stops[si].ID
		}
		if ck.Want == nil {
			res.status = "RECORD"
			res.detail = fmt.Sprintf("order = %s (no golden yet)", strings.Join(got, " -> "))
			return res
		}
		if !sameSeq(got, ck.Want) {
			res.status = "FAIL"
			res.detail = fmt.Sprintf("got %s, want %s", strings.Join(got, " -> "), strings.Join(ck.Want, " -> "))
		} else {
			res.status = "PASS"
			res.detail = fmt.Sprintf("order = %s", strings.Join(got, " -> "))
		}

	case "crosscheck":
		// Re-route in the optimized order as a single call; compare
		// travel time against the matrix-summed prediction.
		if len(opt.Order) == 0 {
			res.status, res.detail = "PASS", "no stops, nothing to cross-check"
			return res
		}
		pts := []geo.Point{t.Origin.Point()}
		for _, si := range opt.Order {
			pts = append(pts, stops[si].At)
		}
		pts = append(pts, t.Dest.Point())
		rr, err := r.Route(ctx, route.ProfileDrive, pts)
		if err != nil {
			res.status, res.detail = "FAIL", "cross-check route: "+err.Error()
			return res
		}
		// matrix-predicted travel time (no dwell): sum legs
		n := len(stops)
		via := 0.0
		prev := n // origin index in matrix
		for _, si := range opt.Order {
			via += m[prev][si]
			prev = si
		}
		via += m[prev][n+1]
		diffPct := math.Abs(via-rr.Duration) / rr.Duration * 100
		if diffPct > ck.MaxPct {
			res.status = "FAIL"
			res.detail = fmt.Sprintf("matrix %.0f s vs route %.0f s (%.1f%% drift > %.0f%%)", via, rr.Duration, diffPct, ck.MaxPct)
		} else {
			res.status = "PASS"
			res.detail = fmt.Sprintf("matrix %.0f s vs route %.0f s (%.1f%% drift)", via, rr.Duration, diffPct)
		}

	default:
		res.status, res.detail = "FAIL", "unknown check type "+ck.Type
	}
	return res
}

// applyRecord fills in goldens.
func applyRecord(ck *Check, direct *route.Route, optNames []string) {
	mins := direct.Duration / 60
	switch ck.Type {
	case "golden_route_min":
		// +/- 10% tolerance band around the observed value.
		ck.GoldMin = math.Floor(mins*0.9/5) * 5
		ck.GoldMax = math.Ceil(mins*1.1/5) * 5
	case "optimize_order":
		ck.Want = append([]string(nil), optNames...)
	}
}

// distFromRoute returns the min distance from p to the route: geometry
// if available, else bbox (conservative: inside bbox => 0).
func distFromRoute(r *route.Route, p geo.Point) float64 {
	if len(r.Geometry) >= 2 {
		return geo.DistToPolylineMeters(p, r.Geometry)
	}
	if !r.BBox.Empty() {
		return r.BBox.DistMeters(p)
	}
	return 0
}

func stopIdx(stops []plan.Stop, id string) (int, bool) {
	for i, s := range stops {
		if s.ID == id {
			return i, true
		}
	}
	return 0, false
}

func sameSeq(a, b []string) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i] != b[i] {
			return false
		}
	}
	return true
}

func fmtDur(sec float64) string {
	m := int(0.5 + sec/60)
	return fmt.Sprintf("%dh%02dm", m/60, m%60)
}

func outcome(failures int) string {
	if failures == 0 {
		return "BENCH PASS"
	}
	return "BENCH FAIL"
}

func fatal(err error) {
	fmt.Fprintln(os.Stderr, "bench error:", err)
	os.Exit(2)
}