package grammar

import (
	"encoding/json"
	"fmt"

	"gitea.maximumdirect.net/eric/audita/internal/core/schema"
	"gitea.maximumdirect.net/eric/audita/internal/framework/contracts"
)

type promptSegment struct {
	ID         int      `json:"id"`
	Speaker    string   `json:"speaker"`
	Start      float64  `json:"start"`
	End        float64  `json:"end"`
	Text       string   `json:"text"`
	Categories []string `json:"categories,omitempty"`
}

type promptTranscriptSection struct {
	SectionIndex int             `json:"section_index"`
	Segments     []promptSegment `json:"segments"`
}

// BuildProposalMessages mirrors the Python grammar-module prompt intent:
// punctuation/capitalization/spacing cleanup only, with strict meaning guards.
func BuildProposalMessages(transcript *schema.Transcript, glossary *schema.Glossary) ([]contracts.LLMMessage, error) {
	glossaryJSON, err := json.MarshalIndent(glossary, "", "  ")
	if err != nil {
		return nil, fmt.Errorf("marshal glossary prompt context: %w", err)
	}

	sectionPayload := promptTranscriptSection{
		SectionIndex: 0,
		Segments:     make([]promptSegment, 0),
	}
	if transcript != nil {
		for _, s := range transcript.Segments {
			sectionPayload.Segments = append(sectionPayload.Segments, promptSegment{
				ID:         s.ID,
				Speaker:    s.Speaker,
				Start:      s.Start,
				End:        s.End,
				Text:       s.Text,
				Categories: append([]string(nil), s.Categories...),
			})
		}
	}

	sectionJSON, err := json.MarshalIndent(sectionPayload, "", "  ")
	if err != nil {
		return nil, fmt.Errorf("marshal transcript prompt context: %w", err)
	}

	system := "You are Audita, a conservative grammar cleanup assistant. Identify only punctuation, capitalization, and spacing cleanup that preserves the same underlying words. Do not change content, substitute words, or rewrite the speaker's phrasing."
	user := "Review this transcript section and return only grammar cleanup corrections that should be applied.\n\n" +
		"Rules:\n" +
		"- Allowed changes are punctuation, capitalization, spacing, and article cleanup only.\n" +
		"- You may add, remove, or adjust commas, periods, quotation marks, apostrophes, dashes, ellipses, spacing, and capitalization when the underlying words stay the same.\n" +
		"- You may change the whole-word article \"a\" to \"an\" or \"an\" to \"a\" when the surrounding text otherwise stays the same.\n" +
		"- Homophone, spoken-form, and mistranscription corrections are handled during a later review stage; do not propose them here.\n" +
		"- Do not make word substitutions, spelling fixes, homophone fixes, filler cleanup, repetition cleanup, paraphrases, or other semantic rewrites.\n" +
		"- Do not change one written word into a different written word, except for capitalization changes to the same letters.\n" +
		"- If a possible correction depends on changing a content word into a different word, omit it here rather than bundling it together with formatting cleanup.\n" +
		"- Treat glossary names and aliases as protected spellings and context.\n" +
		"- Do not replace, Anglicize, normalize, lowercase, or otherwise alter protected glossary names or aliases away from their glossary spelling.\n" +
		"- Preserve canonical glossary capitalization for protected names and aliases, even if they look unusual.\n" +
		"- If a segment includes categories, treat them as additional transcript context.\n" +
		"- Use the exact id from the input segment.\n" +
		"- For returned corrections, original_text must be only the exact text span that needs replacement, not the full segment text unless the whole segment is the replacement span.\n" +
		"- Choose an original_text span that appears exactly once in the current segment text.\n" +
		"- corrected_text must be only the replacement text for that span, not the full corrected segment text unless the whole segment is the replacement span.\n" +
		"- Each returned correction must contain only id, original_text, corrected_text, and confidence.\n" +
		"- Do not return corrections where original_text and corrected_text are identical.\n" +
		"- Do not return speaker, start, or end fields.\n" +
		"- Return only changed segments; do not return entries for unchanged segments.\n" +
		"- confidence must be between 0.0 and 1.0.\n" +
		"- If no corrections are needed, return an empty corrections list.\n\n" +
		fmt.Sprintf("Protected glossary/context:\n%s\n\nTranscript section:\n%s", string(glossaryJSON), string(sectionJSON))

	return []contracts.LLMMessage{
		{Role: "system", Content: system},
		{Role: "user", Content: user},
	}, nil
}