-- Migration 009: Document Extraction and Upload System
-- Adds tables for file upload tracking, AI extraction, and duplicate prevention

-- Table: incoming_files
-- Tracks all uploaded files with SHA256 checksums for duplicate detection
CREATE TABLE IF NOT EXISTS incoming_files (
    file_id SERIAL PRIMARY KEY,
    filename VARCHAR(500) NOT NULL,
    original_filename VARCHAR(500) NOT NULL,
    file_path VARCHAR(1000),
    file_size INTEGER,
    mime_type VARCHAR(100),
    checksum VARCHAR(64) NOT NULL UNIQUE,  -- SHA256 hash for duplicate detection
    status VARCHAR(50) DEFAULT 'pending',  -- pending, processing, processed, failed, duplicate
    uploaded_by INTEGER,  -- Future: REFERENCES users(user_id)
    uploaded_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    processed_at TIMESTAMP,
    error_message TEXT
);

CREATE INDEX idx_incoming_files_status ON incoming_files(status);
CREATE INDEX idx_incoming_files_checksum ON incoming_files(checksum);
CREATE INDEX idx_incoming_files_uploaded_at ON incoming_files(uploaded_at DESC);

-- Table: extractions
-- Stores AI-extracted data from uploaded documents
CREATE TABLE IF NOT EXISTS extractions (
    extraction_id SERIAL PRIMARY KEY,
    file_id INTEGER REFERENCES incoming_files(file_id) ON DELETE CASCADE,
    
    -- Document metadata
    document_type VARCHAR(100),  -- invoice, purchase_order, delivery_note, credit_note
    document_id VARCHAR(100),     -- Invoice/order number extracted by AI
    vendor_name VARCHAR(255),     -- Vendor name extracted by AI
    vendor_cvr VARCHAR(20),        -- CVR number extracted by AI
    vendor_matched_id INTEGER REFERENCES vendors(id),  -- Matched vendor from database
    match_confidence DECIMAL(5,4) CHECK (match_confidence >= 0.0 AND match_confidence <= 1.0),
    
    -- Financial data
    document_date DATE,
    due_date DATE,
    currency VARCHAR(10) DEFAULT 'DKK',
    total_amount DECIMAL(12,2),
    vat_amount DECIMAL(12,2),
    
    -- AI metadata
    confidence DECIMAL(5,4) CHECK (confidence >= 0.0 AND confidence <= 1.0),
    raw_text_snippet TEXT,
    llm_response_json TEXT,       -- Full JSON response from Ollama
    
    -- Processing status
    status VARCHAR(50) DEFAULT 'extracted',  -- extracted, validated, matched, needs_review, converted
    reviewed_by INTEGER,  -- Future: REFERENCES users(user_id)
    reviewed_at TIMESTAMP,
    
    -- Timestamps
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX idx_extractions_file_id ON extractions(file_id);
CREATE INDEX idx_extractions_vendor_matched_id ON extractions(vendor_matched_id);
CREATE INDEX idx_extractions_status ON extractions(status);
CREATE INDEX idx_extractions_document_id ON extractions(document_id);
CREATE INDEX idx_extractions_vendor_cvr ON extractions(vendor_cvr);

-- Table: extraction_lines
-- Stores individual line items extracted from invoices
CREATE TABLE IF NOT EXISTS extraction_lines (
    line_id SERIAL PRIMARY KEY,
    extraction_id INTEGER NOT NULL REFERENCES extractions(extraction_id) ON DELETE CASCADE,
    line_number INTEGER NOT NULL,
    
    -- Product identification
    sku VARCHAR(100),
    ean VARCHAR(13),              -- 13-digit EAN barcode
    description TEXT,
    
    -- Quantities and pricing
    quantity DECIMAL(10,2),
    unit_price DECIMAL(12,4),
    line_total DECIMAL(12,2),
    vat_rate DECIMAL(5,2),        -- VAT percentage (25.00 for 25%)
    vat_amount DECIMAL(12,2),
    
    -- AI metadata
    confidence DECIMAL(5,4) CHECK (confidence >= 0.0 AND confidence <= 1.0),
    
    -- Timestamps
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    
    UNIQUE(extraction_id, line_number)
);

CREATE INDEX idx_extraction_lines_extraction_id ON extraction_lines(extraction_id);

-- Add file_id column to supplier_invoices (link to uploaded file)
ALTER TABLE supplier_invoices 
ADD COLUMN IF NOT EXISTS extraction_id INTEGER REFERENCES extractions(extraction_id);

CREATE INDEX idx_supplier_invoices_extraction_id ON supplier_invoices(extraction_id);

-- Add UNIQUE constraint to prevent duplicate invoices (same vendor + invoice number)
-- Drop existing index if it exists
DROP INDEX IF EXISTS idx_supplier_invoices_vendor_invoice;

-- Create UNIQUE index on vendor_id + invoice_number (simple version without WHERE clause)
CREATE UNIQUE INDEX idx_supplier_invoices_vendor_invoice 
ON supplier_invoices(vendor_id, invoice_number);

-- Trigger to update extractions.updated_at
CREATE OR REPLACE FUNCTION update_extractions_updated_at()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = CURRENT_TIMESTAMP;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

DROP TRIGGER IF EXISTS trigger_update_extractions_updated_at ON extractions;
CREATE TRIGGER trigger_update_extractions_updated_at
    BEFORE UPDATE ON extractions
    FOR EACH ROW
    EXECUTE FUNCTION update_extractions_updated_at();

-- Comments
COMMENT ON TABLE incoming_files IS 'Tracks all uploaded files with SHA256 checksums for duplicate detection';
COMMENT ON TABLE extractions IS 'Stores AI-extracted data from uploaded documents with CVR vendor matching';
COMMENT ON TABLE extraction_lines IS 'Stores individual line items extracted from invoices';
COMMENT ON COLUMN incoming_files.checksum IS 'SHA256 hash of file content - prevents duplicate uploads';
COMMENT ON COLUMN extractions.vendor_cvr IS 'CVR number extracted by AI from invoice';
COMMENT ON COLUMN extractions.vendor_matched_id IS 'Matched vendor from vendors table based on CVR number';
COMMENT ON COLUMN extractions.match_confidence IS 'Confidence score for vendor matching (0.0-1.0)';