package reconcile

import (
	"context"
	"fmt"
	"strings"

	"git.d-ma.be/mathias/tapir/internal/domain"
)

// MaxContested bounds the stored list of contested spots. The counts on the
// Reconciliation are always exact; only this list is capped.
const MaxContested = 200

// Options configure Reconcile. Zero Window and BreakAfter take their defaults.
type Options struct {
	// Window is how many words of the base to show on each side of a dispute. 100 is
	// what was measured (docs/research/local-model-adjudicator-sweep-2026-10-01.md).
	Window int
	// BreakAfter is how many consecutive model errors stop the reconciliation, so a
	// model that is down costs three timeouts, not one per dispute.
	BreakAfter int
	// BaseEngine, AltEngine and Reconciler are recorded on the result.
	BaseEngine, AltEngine, Reconciler string
}

// Reconcile merges two transcripts of the same speech. The base text stands except
// where the model chooses the alternative's reading of a dispute; trivial disputes
// (a compound split, a filler word) are resolved without the model. It never fails a
// transcription: if the model cannot be used the base text comes back unreconciled
// and the result says why. The only error it returns is a cancelled context, which
// is the job stopping, not a verdict on the model.
func Reconcile(ctx context.Context, base, alt domain.Transcription, adj Adjudicator, o Options) (domain.Transcription, error) {
	window, breakAfter := o.Window, o.BreakAfter
	if window <= 0 {
		window = 100
	}
	if breakAfter <= 0 {
		breakAfter = 3
	}
	bt, at := Tokenize(base.Text), Tokenize(alt.Text)
	ds := FindDisputes(bt, at)
	rec := &domain.Reconciliation{
		Status: domain.ReconcileDone, Base: o.BaseEngine, Alt: o.AltEngine, Reconciler: o.Reconciler, Disputes: len(ds),
	}
	seconds := positioner(base, len(bt))

	verdicts := make([]Verdict, len(ds))
	consecutive := 0
	for i, d := range ds {
		if AutoResolve(d) {
			rec.AutoResolved++
			verdicts[i] = VerdictBase
			continue
		}
		if err := ctx.Err(); err != nil {
			return domain.Transcription{}, err
		}
		before, after := ContextAround(bt, d, window)
		v, err := adj.Adjudicate(ctx, Request{Before: before, After: after, Base: d.Base, Alt: d.Alt, AltFirst: i%2 == 1})
		if err != nil {
			if ctxErr := ctx.Err(); ctxErr != nil {
				return domain.Transcription{}, ctxErr
			}
			rec.Errors++
			consecutive++
			if consecutive >= breakAfter {
				return skipped(base, rec, fmt.Sprintf("the model failed %d times in a row: %v", consecutive, err)), nil
			}
			v = VerdictUnsure
		} else {
			consecutive = 0
			rec.Adjudicated++
		}
		verdicts[i] = v
		switch v {
		case VerdictAlt:
			rec.Changed++
			addContested(rec, domain.ContestedSpot{Seconds: seconds(d.BaseStart), Base: d.Base, Alt: d.Alt, Used: "alt"})
		case VerdictUnsure:
			rec.Unsure++
			addContested(rec, domain.ContestedSpot{Seconds: seconds(d.BaseStart), Base: d.Base, Alt: d.Alt, Used: "base", Unsure: true})
		}
	}

	var parts []string
	pos := 0
	for i, d := range ds {
		parts = appendTexts(parts, bt[pos:d.BaseStart])
		if verdicts[i] == VerdictAlt {
			parts = appendTexts(parts, at[d.AltStart:d.AltEnd])
		} else {
			parts = appendTexts(parts, bt[d.BaseStart:d.BaseEnd])
		}
		pos = d.BaseEnd
	}
	parts = appendTexts(parts, bt[pos:])

	out := base
	out.Text = strings.Join(parts, " ")
	out.Reconciliation = rec
	return out, nil
}

// skipped is the base text, none of the partial changes, and the reason.
func skipped(base domain.Transcription, rec *domain.Reconciliation, reason string) domain.Transcription {
	out := base
	out.Reconciliation = &domain.Reconciliation{
		Status: domain.ReconcileSkipped, Reason: reason, Base: rec.Base, Alt: rec.Alt, Reconciler: rec.Reconciler,
		Disputes: rec.Disputes, AutoResolved: rec.AutoResolved, Errors: rec.Errors,
	}
	return out
}

func appendTexts(dst []string, ts []Token) []string {
	for _, t := range ts {
		dst = append(dst, t.Text)
	}
	return dst
}

// positioner maps a token index of the base to the second it starts at: through the
// segments when there are any, proportionally otherwise.
func positioner(base domain.Transcription, tokens int) func(int) float64 {
	if len(base.Segments) == 0 {
		return func(i int) float64 {
			if tokens == 0 {
				return 0
			}
			return float64(i) / float64(tokens) * base.AudioSeconds
		}
	}
	starts := make([]int, len(base.Segments))
	n := 0
	for i, s := range base.Segments {
		starts[i] = n
		n += len(Tokenize(s.Text))
	}
	return func(i int) float64 {
		k := 0
		for k+1 < len(starts) && starts[k+1] <= i {
			k++
		}
		return base.Segments[k].Start
	}
}

func addContested(rec *domain.Reconciliation, c domain.ContestedSpot) {
	if len(rec.Contested) < MaxContested {
		rec.Contested = append(rec.Contested, c)
	}
}