package eval

import (
	"regexp"
	"strconv"
	"strings"
)

// Block header regex. Matches "## A) Role Summary", "## G) Posting Legitimacy", etc.
// Tolerant of extra whitespace and alternate heading text after the letter.
var blockHeaderRE = regexp.MustCompile(`(?m)^##\s+([A-G])\)[^\n]*$`)

// archetypeRE captures "**Archetype:** FDE" style metadata lines.
var archetypeRE = regexp.MustCompile(`(?mi)^\*\*Archetype:\*\*\s*(.+?)\s*$`)

// summaryRE captures the final "**Score:** 4.2/5  **Legitimacy:** High Confidence" line.
// Score and Legitimacy may appear in either order, on one or two lines.
var scoreRE = regexp.MustCompile(`(?mi)\*\*Score:\*\*\s*([0-9]+(?:\.[0-9]+)?)\s*/\s*5`)
var legitRE = regexp.MustCompile(`(?mi)\*\*Legitimacy:\*\*\s*([A-Za-z ]+?)(?:\s*$|\s*\*\*)`)

// weightedScoreRE is the fallback location for the score — Block B's final line.
var weightedScoreRE = regexp.MustCompile(`(?mi)\*\*Weighted score:\*\*\s*([0-9]+(?:\.[0-9]+)?)\s*/\s*5`)

// tierAssessmentRE catches the in-Block-G tier line when the trailing summary
// line is missing: "**Assessment:** Proceed with Caution".
var tierAssessmentRE = regexp.MustCompile(`(?mi)\*\*Assessment:\*\*\s*(.+?)\s*(?:$|\*\*|\n)`)

// ParseEvaluation turns Claude's markdown output into a structured Evaluation.
// Missing blocks yield empty strings rather than errors — the caller decides
// whether incomplete output should be rejected or persisted with a warning.
func ParseEvaluation(raw string) (Evaluation, error) {
	if strings.TrimSpace(raw) == "" {
		return Evaluation{}, errEmpty
	}

	eval := Evaluation{}

	if m := archetypeRE.FindStringSubmatch(raw); len(m) > 1 {
		eval.Archetype = strings.TrimSpace(m[1])
	}

	// Score: prefer final summary line, fall back to Block B weighted score.
	if m := scoreRE.FindStringSubmatch(raw); len(m) > 1 {
		if v, err := strconv.ParseFloat(m[1], 64); err == nil {
			eval.Score = v
		}
	} else if m := weightedScoreRE.FindStringSubmatch(raw); len(m) > 1 {
		if v, err := strconv.ParseFloat(m[1], 64); err == nil {
			eval.Score = v
		}
	}

	// Legitimacy: summary line first, then Block-G Assessment.
	if m := legitRE.FindStringSubmatch(raw); len(m) > 1 {
		eval.Legitimacy = ParseTier(strings.TrimSpace(m[1]))
	} else if m := tierAssessmentRE.FindStringSubmatch(raw); len(m) > 1 {
		eval.Legitimacy = ParseTier(strings.TrimSpace(m[1]))
	}
	if eval.Legitimacy == "" {
		eval.Legitimacy = TierUnknown
	}

	// Split into blocks by heading position.
	headers := blockHeaderRE.FindAllStringSubmatchIndex(raw, -1)
	for i, h := range headers {
		letter := raw[h[2]:h[3]]
		start := h[0]
		end := len(raw)
		if i+1 < len(headers) {
			end = headers[i+1][0]
		}
		body := strings.TrimSpace(raw[start:end])
		switch letter {
		case "A":
			eval.BlockA = body
		case "B":
			eval.BlockB = body
		case "C":
			eval.BlockC = body
		case "D":
			eval.BlockD = body
		case "E":
			eval.BlockE = body
		case "F":
			eval.BlockF = body
		case "G":
			eval.BlockG = body
		}
	}

	// Parse structured stories from Block F.
	eval.Stories = ParseStories(eval.BlockF)

	return eval, nil
}

// storyHeaderRE matches "### Story N:" or "### Story N " headings.
var storyHeaderRE = regexp.MustCompile(`(?m)^###\s+Story\s+\d+[:\s]`)

// starFieldRE matches "**Situation:** ..." style lines.
var starFieldRE = regexp.MustCompile(`(?i)^\*\*([A-Za-z]+):\*\*\s*(.*)$`)

// ParseStories extracts structured STAR stories from Block F markdown.
// Tolerates missing fields and returns an empty slice if the format is not recognized.
func ParseStories(blockF string) []Story {
	if strings.TrimSpace(blockF) == "" {
		return nil
	}

	// Split on story headings, keeping the heading line.
	parts := storyHeaderRE.Split(blockF, -1)
	if len(parts) < 2 {
		// No story headings found.
		return nil
	}

	var stories []Story

	// First element is before the first heading (often empty), skip it.
	for i := 1; i < len(parts); i++ {
		section := parts[i]

		// Extract title from the start (everything before first newline after heading).
		lines := strings.SplitN(section, "\n", 2)
		title := strings.TrimSpace(lines[0])
		// Remove trailing colons.
		title = strings.TrimSuffix(title, ":")

		body := ""
		if len(lines) > 1 {
			body = lines[1]
		}

		story := Story{Title: title}

		// Extract STAR fields from body.
		bodyLines := strings.Split(body, "\n")
		for _, line := range bodyLines {
			if m := starFieldRE.FindStringSubmatch(line); len(m) > 2 {
				field := strings.ToLower(strings.TrimSpace(m[1]))
				value := strings.TrimSpace(m[2])

				switch field {
				case "situation":
					story.Situation = value
				case "task":
					story.Task = value
				case "action":
					story.Action = value
				case "result":
					story.Result = value
				}
			}
		}

		// Only add if at least one field was populated.
		if story.Situation != "" || story.Task != "" || story.Action != "" || story.Result != "" {
			stories = append(stories, story)
		}
	}

	return stories
}

// errEmpty is returned for empty input so the caller can distinguish "nothing
// parsed" from "parsed but missing fields".
var errEmpty = parseError("empty evaluation input")

type parseError string

func (e parseError) Error() string { return string(e) }