package agent

import (
	"errors"
	"strings"

	"reasonix/internal/provider"
)

// currentFinalAssistantAnswer returns visible Content from the current turn.
// It accepts a plain final or the answer immediately before the paired
// update_goal error batch handled without another model round.
func currentFinalAssistantAnswer(sess *Session) string {
	if sess == nil {
		return ""
	}
	msgs := sess.Snapshot()
	if len(msgs) == 0 {
		return ""
	}
	last := msgs[len(msgs)-1]
	if last.Role == provider.RoleAssistant {
		if last.LocalOnly || len(last.ToolCalls) > 0 || strings.TrimSpace(last.Content) == "" {
			return ""
		}
		return last.Content
	}

	resultStart := len(msgs)
	for resultStart > 0 && msgs[resultStart-1].Role == provider.RoleTool {
		resultStart--
	}
	if resultStart == len(msgs) || resultStart == 0 {
		return ""
	}
	assistant := msgs[resultStart-1]
	if assistant.Role != provider.RoleAssistant || assistant.LocalOnly || strings.TrimSpace(assistant.Content) == "" ||
		!updateGoalResultsExactlyMatch(assistant.ToolCalls, msgs[resultStart:]) {
		return ""
	}
	return assistant.Content
}

func updateGoalResultsExactlyMatch(calls []provider.ToolCall, results []provider.Message) bool {
	if len(calls) == 0 || len(calls) != len(results) {
		return false
	}
	seen := make(map[string]struct{}, len(calls))
	for i, call := range calls {
		result := results[i]
		if call.ID == "" || call.Name != "update_goal" || result.Role != provider.RoleTool || result.LocalOnly ||
			result.ToolCallID != call.ID || result.Name != call.Name {
			return false
		}
		if _, duplicate := seen[call.ID]; duplicate {
			return false
		}
		seen[call.ID] = struct{}{}
	}
	return true
}

// salvageReadinessExhaustedAnswer preserves completed writes as unverified.
// It requires a current visible answer and refuses claim-only and typed-report
// runs; the parent still verifies the merged mutation receipts.
func salvageReadinessExhaustedAnswer(sub *Agent, sess *Session, opts Options, err error) (string, bool) {
	var readinessErr *FinalReadinessError
	if !errors.As(err, &readinessErr) || opts.RequireReviewReportKind != "" {
		return "", false
	}
	if sub == nil || !sub.EvidenceSummary().HasMutation() {
		return "", false
	}
	answer := currentFinalAssistantAnswer(sess)
	if answer == "" {
		return "", false
	}
	return "[unverified] The sub-agent finished its work but exhausted the host delivery sign-off checks before reporting (" +
		readinessErr.Reason +
		"). Its successful writes are already on disk and its receipts were merged into this turn's evidence. " +
		"Inspect the diff and run the relevant checks before relying on the result below; do not re-run or \"fix\" the same work without first checking what already changed.\n\nSub-agent answer:\n" +
		answer, true
}