// Package review builds prompts for AI code review and parses LLM responses
// into structured review results.
package review

import (
	"fmt"
	"strings"
)

// outputSchemaJSON is the shared JSON output format specification used by both
// the generic reviewer and persona-based reviewers.
const outputSchemaJSON = `{
  "verdict": "APPROVE" or "REQUEST_CHANGES",
  "summary": "Brief overall assessment (1-3 sentences)",
  "findings": [
    {
      "severity": "MAJOR" or "MINOR" or "NIT",
      "file": "path/to/file",
      "line": <line number from the diff>,
      "finding": "Description of the issue"
    }
  ],
  "recommendation": "Full recommendation text explaining your verdict"
}`

// verdictRules is the shared verdict determination rules.
const verdictRules = `Rules:
- If there are any MAJOR findings → verdict must be REQUEST_CHANGES
- If there are no MAJOR findings → verdict should be APPROVE
- If CI has failed → verdict must be REQUEST_CHANGES with a finding noting the CI failure`

// BuildSystemBase returns the core system prompt instructions without
// patterns or conventions. Used by the budget package to separate
// trimmable from non-trimmable content.
func BuildSystemBase() string {
	var sb strings.Builder

	sb.WriteString("You are an expert code reviewer. Review the provided pull request diff carefully.\n\n")
	sb.WriteString("CONTEXT:\n")
	sb.WriteString("- You will receive the full content of modified files for reference, followed by the diff showing what changed.\n")
	sb.WriteString("- The diff shows ONLY what was added/removed. The full file content provides complete context.\n")
	sb.WriteString("- Focus your review on the CHANGES (the diff), using the full files for context.\n\n")
	sb.WriteString("Your task:\n")
	sb.WriteString("1. Review the diff for correctness, idiomatic code, potential bugs, and design issues.\n")
	sb.WriteString("2. Consider the CI status — if CI has failed, that is an automatic REQUEST_CHANGES regardless of code quality.\n")
	sb.WriteString("3. Output your review as structured JSON (and ONLY JSON, no markdown fences or other text).\n\n")
	sb.WriteString("Output format:\n")
	sb.WriteString(outputSchemaJSON)
	sb.WriteString("\n\n")
	sb.WriteString(verdictRules)
	sb.WriteString("\n- Be thorough but fair. Don't nitpick style unless it impacts readability significantly.\n")
	sb.WriteString("- Line numbers should reference the new file line numbers from the diff headers.\n")
	sb.WriteString("- If the diff is empty or trivial (only formatting/whitespace), APPROVE with no findings.\n")

	return sb.String()
}

// BuildSystemPrompt constructs the full system prompt with patterns and conventions.
// Deprecated: Use BuildSystemBase with budget.Fit for context-aware assembly.
func BuildSystemPrompt(conventions, patterns string) string {
	var sb strings.Builder
	sb.WriteString(BuildSystemBase())

	if patterns != "" {
		sb.WriteString(fmt.Sprintf("\n\n## Language Patterns & Idioms\n\nUse the following patterns as review criteria. Code that violates these established patterns is a finding:\n\n%s\n", patterns))
	}

	if conventions != "" {
		sb.WriteString(fmt.Sprintf("\n\n## Repository Conventions\n\nThe repository has the following coding conventions that must be respected:\n\n%s\n", conventions))
	}

	return sb.String()
}

// BuildUserMeta returns the PR metadata header (title, description, CI status)
// without the diff or file context. Used by the budget package.
func BuildUserMeta(title, description string, ciPassed bool, ciDetails string) string {
	var sb strings.Builder

	sb.WriteString(fmt.Sprintf("## Pull Request: %s\n\n", title))

	if description != "" {
		sb.WriteString(fmt.Sprintf("### Description\n%s\n\n", description))
	}

	ciStatus := "PASSED"
	if !ciPassed {
		ciStatus = "FAILED"
	}
	sb.WriteString(fmt.Sprintf("### CI Status: %s\n", ciStatus))

	if ciDetails != "" {
		sb.WriteString(fmt.Sprintf("CI Details: %s\n", ciDetails))
	}

	return sb.String()
}

// BuildUserPrompt constructs the user message with PR context.
// Deprecated: Use BuildUserMeta with budget.Fit for context-aware assembly.
func BuildUserPrompt(title, description, diff, fileContext string, ciPassed bool, ciDetails string) string {
	var sb strings.Builder

	sb.WriteString(BuildUserMeta(title, description, ciPassed, ciDetails))

	if fileContext != "" {
		sb.WriteString("\n### Full File Context (modified files)\n\n")
		sb.WriteString(fileContext)
		sb.WriteString("\n")
	}

	sb.WriteString("\n### Diff (changes to review)\n\n")
	sb.WriteString("```diff\n")
	sb.WriteString(diff)
	sb.WriteString("\n```\n")

	return sb.String()
}