package config

import (
	"fmt"
	"os"
	"strconv"
)

const (
	DefaultConfigPath         = "/etc/audita/config.yml"
	DefaultConfigPathUsrLocal = "/usr/local/etc/audita/config.yml"
)

var DefaultConfigSearchPaths = []string{
	DefaultConfigPathUsrLocal,
	DefaultConfigPath,
}

func LoadFromEnv() (Config, error) {
	cfg := Default()
	if err := cfg.applyEnvOverrides(os.LookupEnv); err != nil {
		return Config{}, err
	}
	return cfg, nil
}

func loadFromLookup(lookup func(string) (string, bool)) (Config, error) {
	cfg := Default()
	if err := cfg.applyEnvOverrides(lookup); err != nil {
		return Config{}, err
	}
	return cfg, nil
}

func (c *Config) ApplyEnvOverrides() error {
	return c.applyEnvOverrides(os.LookupEnv)
}

func (c *Config) applyEnvOverrides(lookup func(string) (string, bool)) error {
	if c == nil {
		return fmt.Errorf("config must not be nil")
	}

	cfg := c
	if raw, ok := lookup("AUDITA_MODULES"); ok {
		modules, err := ParseModulesCSV(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_MODULES: %w", err)
		}
		cfg.Modules = modules
	}

	primaryLLM := llmTargetPatch{}
	if raw, ok := lookup("AUDITA_LLM_API_KEY"); ok {
		primaryLLM.apiKey = &raw
	} else if raw, ok := lookup("OPENROUTER_API_KEY"); ok {
		primaryLLM.apiKey = &raw
	}
	if raw, ok := lookup("AUDITA_MODEL"); ok {
		primaryLLM.model = &raw
	}
	if raw, ok := lookup("AUDITA_BASE_URL"); ok {
		primaryLLM.baseURL = &raw
	}
	if raw, ok := lookup("AUDITA_LLM_TIMEOUT_SECONDS"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_LLM_TIMEOUT_SECONDS: %w", err)
		}
		primaryLLM.timeoutSeconds = &value
	}
	if raw, ok := lookup("AUDITA_MAX_RETRIES"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_MAX_RETRIES: %w", err)
		}
		primaryLLM.maxRetries = &value
	}
	cfg.applyPrimaryLLMTargetPatch(primaryLLM)

	validationLLM := llmTargetPatch{}
	if raw, ok := lookup("AUDITA_VALIDATION_LLM_API_KEY"); ok {
		validationLLM.apiKey = &raw
	}
	if raw, ok := lookup("AUDITA_VALIDATION_MODEL"); ok {
		validationLLM.model = &raw
	}
	if raw, ok := lookup("AUDITA_VALIDATION_BASE_URL"); ok {
		validationLLM.baseURL = &raw
	}
	if raw, ok := lookup("AUDITA_VALIDATION_LLM_TIMEOUT_SECONDS"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_VALIDATION_LLM_TIMEOUT_SECONDS: %w", err)
		}
		validationLLM.timeoutSeconds = &value
	}
	if raw, ok := lookup("AUDITA_VALIDATION_MAX_RETRIES"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_VALIDATION_MAX_RETRIES: %w", err)
		}
		validationLLM.maxRetries = &value
	}
	cfg.applyValidationLLMTargetPatch(validationLLM)

	concurrency := concurrencyPatch{
		inheritProposal:  true,
		allowLegacyAlias: true,
	}
	if raw, ok := lookup("AUDITA_TOTAL_LLM_CONCURRENCY"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_TOTAL_LLM_CONCURRENCY: %w", err)
		}
		concurrency.totalLLM = &value
	}
	if raw, ok := lookup("AUDITA_LLM_CONCURRENCY"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_LLM_CONCURRENCY: %w", err)
		}
		concurrency.legacyTotalLLM = &value
	}
	if raw, ok := lookup("AUDITA_PROPOSAL_LLM_CONCURRENCY"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_PROPOSAL_LLM_CONCURRENCY: %w", err)
		}
		concurrency.proposalLLM = &value
	}
	if raw, ok := lookup("AUDITA_VALIDATION_LLM_CONCURRENCY"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_VALIDATION_LLM_CONCURRENCY: %w", err)
		}
		concurrency.validationLLM = &value
	}
	cfg.applyConcurrencyPatch(concurrency)

	if raw, ok := lookup("AUDITA_VALIDATION_MAX_PROMPT_TOKENS"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_VALIDATION_MAX_PROMPT_TOKENS: %w", err)
		}
		cfg.ValidationMaxPromptTokens = value
	}

	chunking := chunkingPatch{}
	if raw, ok := lookup("AUDITA_MAX_SECTION_TOKENS"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_MAX_SECTION_TOKENS: %w", err)
		}
		chunking.maxSectionTokens = &value
	}

	if raw, ok := lookup("AUDITA_MIN_SECTION_TOKENS"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_MIN_SECTION_TOKENS: %w", err)
		}
		chunking.minSectionTokens = &value
	}

	if raw, ok := lookup("AUDITA_TARGET_SECTIONS"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_TARGET_SECTIONS: %w", err)
		}
		chunking.targetSections = &value
	}
	cfg.applyChunkingPatch(chunking)

	thresholds := thresholdsPatch{}
	if raw, ok := lookup("AUDITA_GLOSSARY_CONFIDENCE_THRESHOLD"); ok {
		value, err := parseFloat(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_GLOSSARY_CONFIDENCE_THRESHOLD: %w", err)
		}
		thresholds.glossary = &value
	}
	if raw, ok := lookup("AUDITA_GRAMMAR_CONFIDENCE_THRESHOLD"); ok {
		value, err := parseFloat(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_GRAMMAR_CONFIDENCE_THRESHOLD: %w", err)
		}
		thresholds.grammar = &value
	}
	if raw, ok := lookup("AUDITA_HOMOPHONES_CONFIDENCE_THRESHOLD"); ok {
		value, err := parseFloat(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_HOMOPHONES_CONFIDENCE_THRESHOLD: %w", err)
		}
		thresholds.homophones = &value
	}
	if raw, ok := lookup("AUDITA_SPOKEN_WORD_CONFIDENCE_THRESHOLD"); ok {
		value, err := parseFloat(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_SPOKEN_WORD_CONFIDENCE_THRESHOLD: %w", err)
		}
		thresholds.spokenWord = &value
	}
	cfg.applyThresholdsPatch(thresholds)

	normalization := normalizationPatch{}
	if raw, ok := lookup("AUDITA_NORMALIZE_MAX_SEGMENT_GAP"); ok {
		value, err := parseFloat(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_NORMALIZE_MAX_SEGMENT_GAP: %w", err)
		}
		normalization.maxSegmentGap = &value
	}
	if raw, ok := lookup("AUDITA_NORMALIZE_ELLIPSIS_GAP"); ok {
		value, err := parseFloat(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_NORMALIZE_ELLIPSIS_GAP: %w", err)
		}
		normalization.ellipsisGap = &value
	}
	if raw, ok := lookup("AUDITA_NORMALIZE_MAX_SEGMENT_DURATION"); ok {
		value, err := parseFloat(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_NORMALIZE_MAX_SEGMENT_DURATION: %w", err)
		}
		normalization.maxSegmentDuration = &value
	}
	if raw, ok := lookup("AUDITA_NORMALIZE_MAX_SEGMENT_TOKENS"); ok {
		value, err := parseInt(raw)
		if err != nil {
			return fmt.Errorf("AUDITA_NORMALIZE_MAX_SEGMENT_TOKENS: %w", err)
		}
		normalization.maxSegmentTokens = &value
	}
	cfg.applyNormalizationPatch(normalization)

	diagnostics := diagnosticsPatch{}
	if raw, ok := lookup("AUDITA_WORK_DIR"); ok {
		diagnostics.workDir = &raw
	}
	if raw, ok := lookup("AUDITA_WORK_DIR_RETENTION"); ok {
		diagnostics.workDirRetention = &raw
	}
	cfg.applyDiagnosticsPatch(diagnostics)

	cfg.syncLegacyConcurrencyAliases()

	if err := cfg.Validate(); err != nil {
		return err
	}

	return nil
}

func parseInt(raw string) (int, error) {
	value, err := strconv.Atoi(raw)
	if err != nil {
		return 0, fmt.Errorf("must be an integer")
	}
	return value, nil
}

func parseFloat(raw string) (float64, error) {
	value, err := strconv.ParseFloat(raw, 64)
	if err != nil {
		return 0, fmt.Errorf("must be a number")
	}
	return value, nil
}